We believe Ms. Allerton’s qualifications for nomination include her significant experience working for global multinational companies and running complex, international businesses, her extensive knowledge of technology and its successful application to data centers, and her experience as a board member of several large international companies.

Ms. Allerton holds bachelor’s degrees in mathematics from Imperial College, London and in physical sciences and geosciences from the Open University, United Kingdom, a master’s degree in physics from the University of Manitoba, Canada and a master’s degree in finance from the Open University, UK.

10

Table of Contents

CORPORATE GOVERNANCE MATTERS

	PAMELA M. ARWAY		INDEPENDENT
	AGE    69	COMMITTEES Compensation, Nominating and Governance
	DIRECTOR SINCE    2014 Independent Chair since November 2022	OTHER CURRENT PUBLIC COMPANY BOARDS	The Hershey Company DaVita Inc.

Ms. Arway served in a number of capacities during her 21-year career with the American Express Company, Inc., a publicly held global payments, network and travel company, until her retirement in 2008. Ms. Arway served as president, Japan/Asia Pacific/Australia Region, American Express International, Inc., Singapore from October 2005 to January 2008. From December 2004 to October 2005, Ms. Arway served as chief executive officer, American Express Australia Ltd., Sydney, Australia. From July 2000 to December 2004, Ms. Arway served as executive vice president and general manager, Corporate Travel North America, American Express Company, Inc. Ms. Arway has been a director of The Hershey Company, a publicly held company, since May 2010 and has been a director of DaVita Inc., a publicly held company, since May 2009. Ms. Arway also served as a director of Carlson Companies, Inc., a family-owned corporate travel management and private capital company, from May 2019 to July 2021.

We believe Ms. Arway’s qualifications for nomination include her significant leadership experience as a global executive, her expertise in the areas of marketing, international business, finance and government affairs and her experience as a board member of several large publicly held companies.

Ms. Arway holds a bachelor’s degree in languages from Memorial University of Newfoundland and a master’s degree in business administration from Queen’s University, Kingston, Ontario, Canada.

	CLARKE H. BAILEY		INDEPENDENT
	AGE    68 DIRECTOR SINCE    1998	COMMITTEES Audit, Nominating and Governance (chair), Risk and Safety

From June 1999, Mr. Bailey served in various roles of EDCI Holdings, Inc. (“EDCI”) which was taken private in 2010 and was dissolved as of September 2020. Mr. Bailey served as EDCI’s director from June 1999 to September 2020 and as its chief executive officer from July 2009 to September 2020. Mr. Bailey also served as chief executive officer of EDCI from November 2003 to November 2006. In addition, Mr. Bailey served as a director of SMTC Corporation, a publicly held company, from June 2011 to April 2021 and as its non-executive chairman from April 2014 to April 2021. He also served as executive chairman and interim chief financial officer of SMTC Corporation from May 2013 to April 2014.

We believe Mr. Bailey’s qualifications for nomination include his deep industry knowledge and experience gained as the former chief executive officer of Arcus Data Security, an offsite data protection business we acquired in 1998, his understanding of our businesses, operations and strategies as a member of our Board for the past 25 years, his past experience as chairman and chief executive officer of another publicly held company and his service on the boards of directors of other publicly held companies.

Mr. Bailey holds bachelor’s degrees in economics and rhetoric from the University of California at Davis and a master’s degree in business administration from The Wharton School, University of Pennsylvania.

Table of Contents

CORPORATE GOVERNANCE MATTERS

	KENT P. DAUTEN		INDEPENDENT
	AGE    67 DIRECTOR SINCE    1997	COMMITTEES Audit, Finance, Nominating and Governance

Mr. Dauten has served as chairman of Keystone Capital, Inc. (“Keystone”), a private investment firm, since September 2017. Previously, Mr. Dauten served as managing director of Keystone, a position he held since founding the firm in February 1994. Mr. Dauten served as a director of Health Management Associates, Inc., a publicly held hospital management firm, from November 1988 until August 2013.

We believe Mr. Dauten’s qualifications for nomination include his deep industry knowledge and experience as the former president of HIMSCORP, Inc., a records management company we acquired in 1997, his extensive knowledge of the capital markets and business management as the managing director of a private investment business, his understanding of our businesses, operations and strategies as a member of our Board for over 25 years, his financial acumen, his prior service on the board of directors of another publicly held company and his prior experience as our lead independent director.

Mr. Dauten holds a bachelor’s degree in economics from Dartmouth College and a master’s degree in business administration from Harvard Business School.

	MONTE FORD		INDEPENDENT
	AGE    63	COMMITTEES Compensation, Risk and Safety (chair)
	DIRECTOR SINCE    2018	OTHER CURRENT PUBLIC COMPANY BOARDS	Akamai Technologies, Inc. JetBlue Airways Centene Corporation

Mr. Ford has served as principal partner for the CIO Strategy Exchange (“CIOSE”), a cross-industry consortium of 50 chief information officers from large global companies, since May 2015. From May 2013 to September 2013, Mr. Ford served as executive chairman of Aptean, Inc. (“Aptean”), a producer of enterprise software. From April 2012 to April 2013, Mr. Ford served as chief executive officer of Aptean. From February 2012 to March 2012, Mr. Ford served as an advisor to Aptean. Prior to these roles, Mr. Ford served as senior vice president and chief information officer of American Airlines Group from December 2000 to December 2011. Mr. Ford has been a director of Akamai Technologies, Inc., a publicly held content delivery network and cloud service provider, since June 2013 and JetBlue Airways, a publicly held major American airline, since January 2021. Mr. Ford has also been a director of Centene Corporation, a publicly held managed care organization, since November 2022. Mr. Ford served as a director of Michaels Companies, Inc., owner and operator of arts and crafts specialty retail stores, from September 2015 to April 2021.

We believe Mr. Ford’s qualifications for nomination include his extensive experience as an executive in the information technology field, his knowledge related to companies going through a technological transformation, his deep leadership experience and his experience as a board member of large publicly held companies.

Mr. Ford holds a bachelor’s degree in business administration from Northeastern University.

12

Table of Contents

CORPORATE GOVERNANCE MATTERS

	ROBIN L. MATLOCK		INDEPENDENT
	AGE    57	COMMITTEES Compensation, Risk and Safety
	DIRECTOR SINCE    2019	OTHER CURRENT PUBLIC COMPANY BOARDS	MSCI, Inc.

Ms. Matlock served in a number of capacities during her career at VMware, Inc. (“VMware”), a publicly held software virtualization company, until her retirement in January 2021. Ms. Matlock served as a consultant from June 2020 to January 2021 and as senior vice president and chief marketing officer from June 2013 to June 2020. From July 2009 until June 2013, Ms. Matlock served as vice president, corporate marketing of VMware. Prior to these roles, Ms. Matlock served as executive vice president and general manager of Imperva, Inc. from December 2006 to October 2008. Ms. Matlock has served as a director on the board of MSCI, Inc., a publicly held investment research firm, since June 2022. Ms. Matlock has also served as a director of Cohesity, Inc., a privately held software development company, since January 2021, a director of People.ai, a privately held sales software company, since January 2021 and a director of Dremio Corporation, a privately held data lake transformation company, since March 2021.

We believe Ms. Matlock’s qualifications for nomination include extensive experience and executive leadership in global marketing, technology and digital solutions.

Ms. Matlock holds bachelor’s degrees in economics and music from Rice University.

	WILLIAM L. MEANEY
	AGE    62	COMMITTEES None
	DIRECTOR SINCE    2013	OTHER CURRENT PUBLIC COMPANY BOARDS	State Street Corporation

Mr. Meaney assumed the role of our chief executive officer (“CEO”) and, simultaneously, became a member of the Board, in January 2013. Mr. Meaney served as chief executive officer of The Zuellig Group, a private business to business conglomerate, from August 2004 until March 2012. Prior to that position, Mr. Meaney served as Managing Director and Chief Commercial Officer for Swiss International Air Lines, Ltd., a company providing passenger and cargo transportation services in Europe and internationally, from December 2002 to January 2004. Mr. Meaney currently serves on the board of directors of State Street Corporation, a publicly held company that provides financial services to institutional investors. Mr. Meaney served on the board of directors of Qantas Airways Limited, an Australian publicly held company offering passenger and air freight transportation services, from February 2012 to June 2018. Mr. Meaney served on the New York Advisory Board of FM Global, a privately held mutual insurance company, until December 2019. Mr. Meaney served on the board of trustees of Carnegie Mellon University until June 2017 and on the board of trustees of Rensselaer Polytechnic Institute until April 2018.

We believe Mr. Meaney’s qualifications for nomination include his understanding of our businesses, operations and strategies as our current CEO, his extensive experience with global operations and capital allocation and his experience leading a primarily business to business company.

Mr. Meaney holds a bachelor’s degree in mechanical engineering from Rensselaer Polytechnic Institute and a master’s degree in industrial administration from Carnegie Mellon University.

Table of Contents

CORPORATE GOVERNANCE MATTERS

	WENDY J. MURDOCK		INDEPENDENT
	AGE    70	COMMITTEES Compensation (chair), Finance
	DIRECTOR SINCE    2016	OTHER CURRENT PUBLIC COMPANY BOARDS	AvidXchange Holdings, Inc.

Ms. Murdock held a variety of positions with MasterCard Worldwide, including serving as a member of the MasterCard Worldwide Operating Committee, chief payment system integrity officer and chief product officer from 2005 until her retirement in 2013. Since 2013, Ms. Murdock has served on the board of directors of USAA Federal Savings Bank. Ms. Murdock has served on the board of directors of USAA Savings Bank, a subsidiary of USAA Federal Savings Bank, since April 2016. Since March 2016, Ms. Murdock has served on the board of directors of La Caisse de dépôt et placement du Québec, an institutional investor that manages pension plans and insurance programs in Quebec. Since October 2021, Ms. Murdock has served on the board of AvidXchange Holdings, Inc., a publicly held account payable automation software and payment solutions company. From December 2013 to May 2016, Ms. Murdock served as a non-executive director of Recall Holdings Limited, a publicly held information management company we acquired in 2016.

We believe Ms. Murdock’s qualifications for nomination include her deep industry knowledge and experience gained as a non-executive director of Recall Holdings Limited, her significant leadership experience as a global executive and her expertise in the areas of international business and finance.

Ms. Murdock holds a bachelor’s degree from McGill University and a master’s degree in business administration from the University of Western Ontario.

	WALTER C. RAKOWICH		INDEPENDENT
	AGE    65	COMMITTEES Audit (chair), Finance, Nominating and Governance
	DIRECTOR SINCE    2013	OTHER CURRENT PUBLIC COMPANY BOARDS	Host Hotels & Resorts, Inc., a publicly held company. Mr. Rakowich holds a Bachelor of Science degree in accounting from Pennsylvania State University and a Master of Business Administration degree from Harvard Business School. We believe Mr. Rakowich's qualifications for nomination include valuable industry knowledge and management expertise that Mr. Rakowich has developed as CEO of an industrial REIT, as well as his corporate finance and accounting expertise. Ventas, Inc.

Mr. Rakowich served as chief executive officer of Prologis Inc. (“Prologis”), a publicly held logistics real estate investment trust (“REIT”), from November 2008 through June 2011, when Prologis merged with AMB Property Corporation (with the merged company being named Prologis), after which he assumed the role of co-chief executive officer and served as a member of the Prologis board of directors until he retired in December 2012. Mr. Rakowich held a number of senior management positions while at Prologis before becoming chief executive officer, including managing director and chief financial officer from December 1998 to January 2005 and president and chief operating officer from January 2005 to November 2008. Mr. Rakowich served on the Prologis board of trustees from January 2005 through June 2011. Mr. Rakowich is a member of the board of directors of Host Hotels & Resorts, Inc. and Ventas, Inc., each of which is a publicly held REIT.

We believe Mr. Rakowich’s qualifications for nomination include valuable industry knowledge and management expertise that Mr. Rakowich has developed as chief executive officer of an industrial REIT, his corporate finance and accounting expertise and his experience as a member of the board of directors of other publicly held REITs.

Mr. Rakowich holds a bachelor’s degree in accounting from Pennsylvania State University and a master’s degree in business administration from Harvard Business School.

Alfred J. Verrecchia Age 7314

Table of Contents

CORPORATE GOVERNANCE MATTERS

	Mr. Verrecchia became a member of our Board in March 2010 and has served as our Independent Chairman since March 2013. Mr. Verrecchia served as chairman of the board of directors of Hasbro, DOYLE R. SIMONS		INDEPENDENT
	AGE    59	COMMITTEES Compensation, Finance (chair)
	DIRECTOR SINCE    2020	OTHER CURRENT PUBLIC COMPANY BOARDS	Fiserv, Inc., or Hasbro, a publicly held branded play company, from May 2008 to May 2015. He was the president and chief executive officer of Hasbro from 2003 until 2008, and prior to that he served as Hasbro's chief operating officer and chief financial officer. Mr. Verrecchia has served on the board of directors of several publicly held companies, including Old Stone Corp. from 1987 to 2012, FGX International Holdings Limited from February 2009 to March 2010 and CVS Caremark from September 2004 to March 2007. Mr. Verrecchia holds both a Bachelor of Arts degree in accounting and a Master of Business Finance degree, each from the University of Rhode Island. We believe Mr. Verrecchia's qualifications for nomination include his strong understanding and insights related to the operation of an enterprise in both the U.S. and international markets as the current chairman and former chief executive officer and president of a multinational publicly held corporation, his experience transforming a traditional product business, his extensive understanding of the capital markets and accounting as a former chief financial officer, his experience as a member of the board of directors of other publicly held companies and his prior experience as our lead independent director.

Mr. Simons served as president and chief executive officer of Weyerhaeuser Co. (“Weyerhaeuser”), a publicly held timber REIT, from August 2013 until his retirement in December 2018. Prior to this role, Mr. Simons served as chairman and chief executive officer of Temple-Inland, a publicly held corrugated packaging and building products company, from December 2007 to February 2012. Mr. Simons has served on the board of directors of Fiserv, Inc., a publicly held global provider of financial services technology, since 2007. Mr. Simon served on the board of Weyerhaeuser from June 2012 to December 2018 and on the board of Temple-Inland from January 2008 to February 2012.

We believe Mr. Simons qualifications for nomination include valuable industry knowledge and management expertise that Mr. Simons developed as an executive of a publicly held REIT, as well as his strong skills in corporate finance and strategic planning.

Mr. Simons holds a bachelor’s degree in business administration from Baylor University and a juris doctor from the University of Texas.

SELECTION OF DIRECTOR NOMINEES

The Nominating and Governance Committee is responsible for identifying and recommending to the Board qualified candidates for nomination by the Board at each annual meeting of stockholders, consistent with the criteria set forth in our Board-approved corporate governance guidelines (our “Corporate Governance Guidelines”). The Board annually electsis responsible for nominating qualified candidates for election at each annual meeting of stockholders and for filling vacancies on the officersBoard that may occur between annual meetings of the Company. Each officer holds office atstockholders.

The Nominating and Governance Committee considers several factors when evaluating candidates to be nominated to the discretionBoard, including integrity, experience, achievements, judgment, intelligence, personal character, ability to make independent analytical inquiries, willingness to devote adequate time to Board duties and likelihood that each candidate will be able to serve on the Board for a sustained period. In connection with the selection of nominees for director, the Board’s policy is to give due consideration to the Board’s overall balance of diversity of perspectives, backgrounds and experiences. To implement and review the effectiveness of our diversity policy, the Nominating and Governance Committee reviews the appropriate skills and characteristics of members of the Board untilin the first meetingcontext of the then current composition of the Board.

The Board will not nominate any candidate who has not agreed to tender, promptly following the annual meeting at which such candidate is elected, an irrevocable resignation that will be effective upon (1) the failure to receive the required number of votes at the next annual meeting of stockholders at which such candidate faces re-election, and (2) the acceptance of such resignation by the Board.

The Nominating and Governance Committee considers director nominees who are properly recommended by stockholders for election to the Board at a meeting of stockholders at which directors are to be elected. To be proper, a director nominee recommendation must comply with applicable law, the Company’s Bylaws and the Company’s Corporate Governance Guidelines. The Nominating and Governance Committee will consider, and evaluate in the same manner, any suggestions offered by directors or until such officer sooner dies, resigns or is removed. Therestockholders with respect to potential director nominees. However, the Nominating and Governance Committee and the Board are no family relationships between or among anynot required to enlarge the size of the Company's officersBoard in order to nominate an otherwise fully qualified candidate proposed by a stockholder. A stockholder wishing to nominate a director directly must comply with the procedures described in the Company’s Bylaws and this Proxy Statement.

Table of Contents

CORPORATE GOVERNANCE MATTERS

STOCKHOLDER PROPOSALS

A stockholder that wants to include a proposal in the Company’s proxy materials for consideration at the 2024 Annual Meeting of Stockholders pursuant to Rule 14a-8 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), must submit the proposal to the Company (i) by December 1, 2023 and (ii) in accordance with certain eligibility standards and regulations established by the SEC and our Bylaws. A stockholder who intends to present a proposal at the 2024 Annual Meeting of Stockholders without inclusion of such proposal in the proxy materials must provide notice in accordance with Section 2.4 or directors.

        Set forth below is the name and age of eachSection 3.2 of our Bylaws, which require that notice of the proposal be received at our principal executive officersoffice no earlier than January 10, 2024 and no later than February 9, 2024. However, if the date of our 2024 Annual Meeting of Stockholders occurs more than 30 days before or 30 days after May 9, 2024, the anniversary of the 2023 Annual Meeting of Stockholders, a stockholder notice will be timely if it is received at our principal executive office by the later of (1) the 120th day prior to such annual meeting or (2) the close of business on the tenth day following the day on which public disclosure of the date of the meeting was made. To be in proper form, a stockholder’s notice must include the specified information concerning the stockholder and the business proposal or nominee, as described in Sections 2.4, 3.2 and 3.3 of our Bylaws and must be mailed to the Company’s principal executive office, at the address stated herein, and should be directed to the attention of the Secretary of the Company.

NOMINATIONS OF INDIVIDUALS FOR ELECTION AS DIRECTORS USING PROXY ACCESS

A stockholder, or group of up to 20 stockholders, that has owned continuously for at least three years shares of our stock representing an aggregate of at least 3% of the total voting power of our outstanding shares entitled to vote in the election of directors, may nominate and include in our proxy materials director nominees constituting up to the greater of two or 20% of our Board (the “Proxy Access Director Nominees”), provided that the stockholder(s) and nominee(s) satisfy the requirements in our Bylaws. Notice of the Proxy Access Director Nominees must be received at our principal executive office no earlier than 150 calendar days, and no later than 120 calendar days, prior to the first anniversary of the date of the Company’s proxy statement released to stockholders in connection with the previous year’s annual meeting of stockholders.

STOCKHOLDER SOLICITATION OF PROXIES IN SUPPORT OF DIRECTOR NOMINEES OTHER THAN COMPANY NOMINEES

In addition to satisfying the applicable provisions of our Bylaws, including the deadline for written notices, and the requirements of Rule 14a-19 under the Exchange Act, stockholders who is not nominatedintend to solicit proxies in support of director nominees other than the Company’s nominees must provide notice that sets forth the information required by Rule 14a-19 no later than March 10, 2024. If the date of the 2024 Annual Meeting changes by more than 30 calendar days from the date of the Annual Meeting, such notice must instead be provided by the later of 60 calendar days prior to the date of the 2024 Annual Meeting or the 10th calendar day following public announcement by the Company of the date of the 2024 Annual Meeting.

BOARD AND COMMITTEE EVALUATIONS

The Nominating and Governance Committee annually establishes and oversees the Board and committee evaluation process. Generally, the Board and each committee conduct self-evaluations by means of written questionnaires completed anonymously by each director and committee member. The responses are summarized and provided to the Board and each committee at their subsequent meetings for discussion and review. Historically, the Nominating and Governance Committee has from time to time engaged an independent third-party firm to conduct a directorcomprehensive independent evaluation of the Board, the committees and individual directors, and we plan to continue this practice in the future.

16

Table of Contents

CORPORATE GOVERNANCE MATTERS

BOARD STRUCTURE

BOARD LEADERSHIP STRUCTURE

The Board believes that Iron Mountain stockholders are best served by the Board having flexibility to consider and determine the best leadership structure for the Company, including whether the roles of Chair of the Board (“Chair”) and CEO should be combined or separated, based on current relevant facts and circumstances rather than by adhering to a formal standing policy on the subject.

The Board has determined that the current position of Chair should be held by an independent non-employee of the Company. The Board believes this structure fosters effective governance and oversight of the Company, his orand allows the CEO to focus on strategic planning and execution of our day-to-day performance while the Chair leads the Board in its fundamental role of providing advice and oversight to management. Among other things, the Chair’s duties include:

The Board believes this governance structure promotes balance between the authority of those who oversee our business and those who manage it on a day-to-day basis. A non-management executive session is offered before the conclusion of each Board and committee meeting, which further facilitates the independence of our Board. The current Chair has established strong working relationships with her principal occupationfellow Board members and business experience during the past five yearshas garnered their confidence and the names of certain other companies of which he or she servedrespect.

There may however be unique circumstances, such as a change in executive or Board composition or a significant strategic development, under which the Board may determine that stockholders are best served by combining the roles of Chair and CEO and appointing a strong lead independent director aswith robust duties and responsibilities. In the event that the roles of April 15, 2016.

Board of Directors and Committeeswould appoint a strong lead independent director with a well-defined role similar to the responsibilities undertaken by our current Chair. We anticipate that we would disclose any such change in our Board leadership structure to the stockholder community.

        Independence.INDEPENDENCE

Our Board is composed of a majority of directors who qualify as independent directors pursuant to the corporate governance standards for companies listed on the NYSE.New York Stock Exchange (“NYSE”). The Board evaluates independence pursuant to NYSE standards each year by affirmatively determining whether each director has a direct or indirect material relationship with the Company (including its subsidiaries) andor members of the Company'sCompany’s management that may interfere with such director'sdirector’s ability to exercise his or her independence from the Company. When assessing the materiality of a director'sdirector’s relationship with the Company, the Board considers all relevant facts and circumstances, not merely from the director'sdirector’s standpoint but from that of the persons or organizations with which the director has an affiliation. Material relationships can include commercial, industrial, banking, consulting, legal, accounting, charitable and familial relationships. None of our independent directors (other than Mr. Deninger) has any relationship with the Company or its management other than his or her service as a director and on committees of the Board, and the Board has concluded that none of the Company'sCompany’s directors possess the objective relationships set forth in the NYSE listing standards that prevent independence.

        In assessingWhen evaluating the independence of Mr. Deninger,director nominees, the Board considered Mr. Deninger's position as a senior managing director at Evercore Partners Inc., or Evercore. In 2013weighs numerous factors, including the Company entered into an agreement with Evercore pursuant to which Evercore agreed to provide financial advisory services to the Company, as further described under the "Certain Relationships and Related Transactions" sectioneffect of this Proxy Statement. In 2015 the Company paid the final $250,000multiple years of fees associated with the agreement with Evercore. The agreement with Evercore has terminated in accordance with its terms. The Board determined that, because Mr. Deninger agreed to waive any direct fees he may receive in connection with the Evercore engagement and did not workservice on the engagement on behalfability of Evercore, this relationship would not interfere with Mr. Deninger's abilityour director nominees to exercise independence from the Company.

maintain independence. The Board has determined that all of our non-management directors who served in 2022 and who are nominated as directors qualify as independent under NYSE rules. One of our directors, Mr. Meaney, is a management employee involved in our day-to-day activities and is not considered to be an independent director.

        Attendance.BOARD MEETING ATTENDANCE

During the fiscal year ended December 31, 2015,2022, the Board held 13seven meetings. EachIn 2022, each incumbent director attended at least 75% of the aggregate number of meetings of the Board and allthe committees thereof on which such director served that were held during the period for whichwhile such

incumbent director served. Mr. Chatfield and Ms. Murdock are expected to joinserved on the Board on May 2, 2016 and did not attend any Board and committee meetings duringor the fiscal year ended December 31, 2015. All of ourrespective committees. Nine (9) directors standing for re-election at the timein 2023 attended our 2015virtual 2022 Annual Meeting of Stockholders. All directors standing for re-election are expected to attend the Annual Meeting, either in person or by teleconference. Our policy with respect to directors'directors’ attendance at our annual meetings of stockholders can be found in our Corporate Governance Guidelines, the full text of which appears under the heading "Company/Investors/“Investors/Corporate Governance"Governance/Governance Documents” on our website at www.ironmountain.com.

Board Leadership StructureBOARD COMMITTEES

        The Board does not have a formal policy as to whether the roles of Chairman and CEO should be combined or separated. The Board believes that Iron Mountain stockholders are best served by the Board having flexibility to consider the relevant facts and circumstances and determine, at the time of the Chairman's election, the best leadership structure for the Company rather than by adhering to a formal standing policy on the subject.

        As a result of the Board's ongoing review of its leadership structure, the Board has determined that the position of Chairman should be held by a non-employee of the Company. The Board believes that the current leadership structure, which separates the roles of CEO and Independent Chairman, fosters effective governance and oversight of the Company. The Independent Chairman controls the Board meeting agendas, which ensures that topics deemed important by the independent directors are included in Board discussions and best enables the Board to express its views on our management, strategy and execution. The Independent Chairman is responsible for advising the CEO and presiding over meetings of the Board, presiding over all executive sessions of non-management directors, consulting with the CEO on Board meeting agendas and acting as a liaison between management and non-management directors. The CEO is responsible for setting the Company's strategy and leading the organization's day-to-day performance. We believe this governance structure promotes balance between the authority of those who oversee our business and those who manage it on a day-to-day basis.

        The Board convenes in non-management executive session before the conclusion of each in-person Board meeting, and an executive session is offered in all telephonic Board meetings.

Committees

The Board has the following standing committees: Audit Committee, Compensation Committee, Nominating and Governance Committee, Finance Committee and Risk and Safety Committee. The Technology Committee, which was formed in October 2020, was dissolved in May 2022, and its responsibilities were returned to the Board. The Board and management have assigned specific areas of risk oversight to each standing committee. The Board has adopted a charter for each of its standing committees, and each such charter is available on our website at www.ironmountain.com under the heading "Company/Investors/“Investors/Corporate Governance."Governance/Governance Documents.” During the fiscal year ended December 31, 2015,2022, the Audit Committee held sixfour meetings, the Compensation Committee held sixfive meetings, the Nominating and Governance Committee held fivethree meetings, the Finance Committee held ninefour meetings and the Risk and Safety Committee held sixthree meetings. In 2022, each incumbent director who served on a Board committee attended at least 75% of that committee’s meetings held during the period such incumbent director served on that committee.

The Nominating and Governance Committee annually reviews the composition of the Board committees and considers whethertypically makes changes to recommend committee membership changes to the Board. In 2015 the Nominatingeach year and Governance Committee, in an effort to promote continuity, did not recommend any committee membership changes.

        Membership on each committee generally has a mix of directors who have previously served on the committee and directors who have not previously served on the committee. Committee membership as set forth below is as of April 15, 2016 is set forth in the chart below.

Committee Membership
March 30, 2023.

Upon the consummation of the Company's acquisition of Recall, each of Mr. Chatfield's appointment to the Board and Ms. Murdock's appointment to the Board will become effective. Mr. Chatfield is expected to join the Audit Committee and the Risk and Safety Committee, and Ms. Murdock is expected to join the Compensation Committee and the Finance Committee.

ROLES AND RESPONSIBILITIES

        Audit Committee.    Each member of the Audit Committee is independent as defined by the rules of the SEC, the NYSE listing standards and the Audit Committee Charter. In addition, the Board has determined that each member of the Audit Committee is an audit committee financial expert as defined by the rules of the SEC and is financially literate as defined by the NYSE listing standards. The Audit Committee: (1) assists the Board in oversight of the integrity of the Company's financial statements; (2) assists the Board in oversight of the Company's compliance with legal and regulatory requirements; (3) assists the Board in oversight of the independent registered public accounting firm's retention, qualifications and independence; (4) assists the Board in oversight of the performance of the Company's internal audit function and independent auditors; (5) prepares an Audit Committee report as required by the SEC to be included in the annual Proxy Statement; (6) performs such other duties as the Board may assign to the Audit Committee from time to time, such as approving transactions subject to our Related Person Transaction Policies and Procedures described on page 73 of this Proxy Statement; and (7) takes other actions to meet its responsibilities as set forth in its written charter.

The Audit Committee is also responsible for establishing procedures for the receipt, retention and treatment of complaints regarding accounting, internal accounting controls and auditing matters, including procedures for the confidential and anonymous submission by employees of the Company of any concerns regarding accounting or auditing matters they think may be questionable. Information about these procedures can be found in our Code of Ethics, which is available on our website, www.ironmountain.com, under the heading "Company/Investors/“Investors/Corporate Governance."Governance/Governance Documents.”

        Compensation Committee.    Each member

18

---

Table of the Compensation Committee qualifies as independent under the NYSE listing standards. Contents

CORPORATE GOVERNANCE MATTERS

COMPENSATION COMMITTEE		5 Meetings in 2022
CHAIR Murdock	MEMBERS Arway Ford Matlock Simons	Each member of the Compensation Committee qualifies as independent under the applicable NYSE listing standards, SEC rules and the Board’s independent assessment.

ROLES AND RESPONSIBILITIES

The Compensation Committee: (1) reviews, approves and recommends to the independent members of the Board the base salary, equity-based incentives and the payment of short-term incentive compensation for the CEO; (2) approves all long-term equity incentives to our employees, including Messrs. Day, Duale, Meaney and Keddy and Ms. Evens, or, collectively, the Named Executive Officers, under the 2014 Stock and Cash Incentive Plan, or the 2014 Plan; (3) reviews and approves the annual cash compensation for Named Executive Officers (other

than the CEO) based on recommendations from the CEO and reports to the Board on such decisions; (4) reviews the Company's cash and stock-based incentive compensation plans to assess their effectiveness in meeting the Company's goals and objectives and exercises all of the authority of the Board with respect to the administration of such plans; (5) annually reviews and discusses with management a draft of the Company's Compensation Discussion and Analysis to be included in the Company's Annual Report on Form 10-K and annual proxy statement; (6) annually prepares and publishes an annual report of the Compensation Committee for inclusion in the Company's Annual Report on Form 10-K and annual proxy statement; (7) reviews and discusses at least on an annual basis the risks arising from the Company's compensation policies for its employees; and (8) takes other actions to meet its responsibilities as set forth in its written charter.

The Board has delegated final authority for compensation decisions for the Named Executive Officers,executive officers, other than our CEO, to the Compensation Committee. The Compensation Committee has the authority, as it deems appropriate, to delegate any of its responsibilities to a sub-committee composed of members ofand has delegated the Compensation Committee, but it hasauthority to the CEO to approve within an approved budget long-term equity incentive grants below maximum thresholds to employees who are not done so to date.executive officers or senior vice presidents.

For a discussion concerning the process and procedures for determining executive compensation and the role of executive officers and compensation consultants in determining or recommending the amount or form of compensation, see the "Compensation“Compensation Discussion and Analysis"Analysis” section in this Proxy Statement.

---

Table of Contents

CORPORATE GOVERNANCE MATTERS

NOMINATING AND GOVERNANCE COMMITTEE			3 Meetings in 2022
CHAIR Bailey	MEMBERS Arway Dauten Rakowich Verrecchia	Each member of the Nominating and Governance Committee qualifies as independent under the applicable NYSE listing standards, SEC rules and the Board’s independent assessment.

ROLES AND RESPONSIBILITIES

The Nominating and Governance Committee.    Each memberCommittee:

20

---

Table of Contents

CORPORATE GOVERNANCE MATTERS

FINANCE COMMITTEE		4 Meetings in 2022
CHAIR Simons	MEMBERS Dauten Murdock Rakowich	Although the NYSE listing standards do not require a standing finance committee or that any such committee be comprised exclusively of independent members, all members of the Finance Committee qualify as independent under the applicable NYSE listing standards, SEC rules and the Board’s independent assessment.

ROLES AND RESPONSIBILITIES

The Finance Committee:

1.	reviews and provides recommendations with respect to the Company’s capital structure, leverage and financial strategies;
2.	reviews the Company’s material capital allocation decisions, strategic investments and dispositions and other opportunities for maximizing stockholder value and periodically reviews and evaluates the performance of and returns on investments and dispositions approved by the Board;
3.	considers, reviews and provides recommendations to the Board with respect to the Company’s dividend and share repurchase policies and programs and other strategies to return capital to stockholders;
4.	reviews and approves the Company’s derivatives and hedging policies and strategies;
5.	reviews the Company’s investment policies and practices;
6.	reviews the Company’s credit ratings and strategy;
7.	periodically reviews the Company’s investor relations strategy;
8.	furnishes periodic reports to the Board concerning the Finance Committee’s work; and
9.	performs such other duties as the Board may assign to the committee from time to time.

RISK AND SAFETY COMMITTEE			3 Meetings in 2022
CHAIR Ford	MEMBERS Allerton Bailey Matlock	Although the NYSE listing standards do not require a standing risk and safety committee or that any such committee be comprised exclusively of independent members, all members of the Risk and Safety Committee qualify as independent under the applicable NYSE listing standards, SEC rules and the Board’s independent assessment.

ROLES AND RESPONSIBILITIES

The Risk and Safety Committee:

1.	based on reports provided by the Company’s management, monitors (i) the adequacy of material fire, health, safety, security, business continuity, cyber security, chain of custody and information security and risk management strategies and systems for the reporting of accidents, incidents and risks, and (ii) material investigations and remedial actions, as appropriate;
2.	reviews the Company’s establishment and operation of its enterprise-wide risk management (“ERM”) program which is designed to identify, assess, monitor and manage risk throughout the Company, and includes an annual management ERM report to the Board;
3.	monitors the Company’s insurance program;
4.	furnishes periodic reports to the Board concerning the Risk and Safety Committee’s work; and
5.	examines any other matters referred to it by the Board.

2022 PROXY STATEMENT	21

---

Table of Contents

CORPORATE GOVERNANCE MATTERS

THE BOARD’S ROLE, RESPONSIBILITIES AND POLICIES

THE BOARD’S ROLE IN RISK OVERSIGHT

We have a comprehensive ERM which is designed to identify, assess, monitor and manage risk throughout the Company, with the Board exercising oversight responsibility for risk both directly and through standing committees.

OUR BOARD OF DIRECTORS The Board reviews and discusses with management significant risks affecting the Company, including matters escalated by its committees within their respective areas of oversight. The Board also formally reviews the Company’s overall risk position and risk management processes at least annually, which allows the Board and each of its committees to remain coordinated in overseeing enterprise risk. Further, our independent Chair ensures that important topics, including those relating to risk matters, are included as topics for discussion by the Board. Although management, including our CEO, and the Board and its committees work together on risk matters, the Board has the ultimate oversight authority. The Board also reviews the Company’s ethics and compliance program annually. The Board reserves the right to and periodically does consult with outside advisors and experts from time to time to assist the Board in anticipating future threats and trends. OUR BOARD COMMITTEES The Nominating and Governance Committee periodically reviews the allocation of risk oversight among the Board’s committees. Each committee focuses on specific aspects of enterprise risk, emerging risk trends and ad-hoc risk issues in the areas of risk allocated to it. In coordination with the Board, the Nominating and Governance Committee also periodically reviews environmental, social and governance (“ESG“) strategy and initiatives. The Risk and Safety Committee reviews and monitors fire, health, safety, security, business continuity, cybersecurity, chain of custody and information security and risk management strategies, systems and policies and processes implemented, established and reported on by management. The Risk and Safety Committee also has the primary responsibility for assisting the Board with oversight of the Company’s ERM program, which is designed to identify, assess, monitor and manage risk throughout the Company, and includes an annual management ERM report to the Board. The Audit Committee oversees, among other things, (i) the integrity of the Company’s financial statements and financial reporting process, (ii) the performance of the Company’s internal audit function and independent auditors, and (iii) the receipt, retention and treatment of complaints received by the Company regarding accounting, internal accounting controls or auditing matters. The Audit Committee also assists the Board in overseeing the Company’s compliance with legal and regulatory requirements. The Compensation Committee oversees the executive compensation program throughout the year with the assistance of an independent compensation consultant and also reviews and discusses the risks arising from the Company’s compensation policies and practices. During each regularly scheduled Board meeting, each committee chair provides a summary to the Board of his or her committee’s risk discussions since the most recent regularly scheduled Board meeting. The key responsibilities of each standing committee of the Board and the risk oversight of such committees are further detailed on pages 18 through 21. OUR MANAGEMENT TEAM Our management team, with oversight from the Board, is responsible for the Company’s risk management process and the day-to-day supervision and mitigation of enterprise risks. Our ERM program includes the receipt by our executive team of regular reports from our operations personnel. Our executive team has established an enterprise risk committee which includes each of our executive vice presidents and is chaired by our Chief Risk Officer. The enterprise risk committee oversees our risk and compliance activities, ensuring that management has appropriate policies, structures and systems in place for managing risks of the business. We also maintain an enterprise risk steering committee and regional risk committees which review risk trends and emerging risks to our business and report risk topics to our enterprise risk committee. Through their participation in our enterprise risk committee, our executive team reviews and prioritizes significant risks, allocates resources for mitigation and provides the Board with regular reports on areas of potential Company risk, including strategic, operational, information security, human resources, financial, legal, compliance, REIT and regulatory risks.

22

---

Table of Contents

CORPORATE GOVERNANCE MATTERS

Each of the Board’s standing committees has been assigned the oversight of certain identified risks, and the Board, or the committee of the Board assigned responsibility for a specific area of risk, receives updates from the Company executive accountable for understanding and mitigating each such identified risk. The Company’s Chief Risk Officer, who reports to the Chief Operating Officer, is responsible for the day-to-day oversight of the risk management program. The Chief Risk Officer provides an ERM report at each meeting of the Risk and Safety Committee. The ERM report addresses short-term and long-term enterprise risks, risk trends and noteworthy incidents. The Company’s Chief Compliance Officer, who reports to the General Counsel, is responsible for the development, review, and execution of the Company’s compliance and business conduct program and, with the General Counsel, regularly reports to the Board and the Audit Committee. The Company also consults with outside advisors as necessary to identify and understand emerging risks. OUR INTERNAL AUDIT TEAM The internal audit team, under the direct supervision of the Audit Committee, identifies and helps mitigate risk, and assesses and improves the Company’s internal controls. The internal audit team accesses the Company’s disclosure controls and procedures and reports any material weaknesses or significant deficiencies to the Audit Committee. At each meeting of the Audit Committee, the Vice President of Internal Audit and the Chief Compliance Officer meet with the Audit Committee in closed session.

2022 PROXY STATEMENT	23

---

Table of Contents

CORPORATE GOVERNANCE MATTERS

THE BOARD’S ROLE IN MANAGEMENT SUCCESSION

The Board oversees the recruitment, development, and retention of executive talent. Management succession is generally discussed throughout the year with the CEO at Board meetings and in executive sessions. Management succession discussions generally focus on the CEO and other senior executive roles and also include broader discussions about the Company’s workforce. The Board has regular and direct exposure to senior leadership and high-potential employees through meetings held throughout each year.

STOCKHOLDER COMMUNICATIONS WITH THE BOARD

The Board believes it is important to engage effectively with stockholders and maintains a written Stockholder Engagement and Communication Policy (the “Stockholder Engagement Policy”), which outlines the procedures for the Board’s engagement and communication with the Company’s stockholders. The Stockholder Engagement Policy is overseen by the Nominating and Governance Committee qualifiesCommittee. Under the Stockholder Engagement Policy, any stockholder, security holder or other interested party who desires to communicate with the Board, any individual director, including the Chair, or the independent or non-management directors as independent undera group, may do so by regular mail or email directed to the NYSE listing standards. Secretary of the Company. Communications to the Board should be mailed to Corporate Secretary, Iron Mountain Incorporated, One Federal Street, Boston, Massachusetts 02110; the Secretary’s email address is corporatesecretary@ironmountain.com. Upon receiving such mail or email, the Secretary will assess the appropriate director or directors to receive the message and will forward the mail or email to such director or directors without editing or altering it.

CORPORATE GOVERNANCE GUIDELINES

The NominatingBoard maintains our Corporate Governance Guidelines that describe our corporate governance practices and policies and provide a framework for our Board governance. The topics addressed in our Corporate Governance Committee: (1) recommends theGuidelines include: composition and selection of the Board; (2) identifiesdirector responsibilities; Board meetings; Board committees; director access to management and recommends candidatesindependent advisors; director compensation; executive compensation clawback; director orientation and continuing education; management evaluation and succession; the Board’s annual performance evaluation and conflicts of interest. Our Corporate Governance Guidelines are available on our website, www.ironmountain.com, under the heading “Investors/Corporate Governance/Governance Documents.”

INSIDER TRADING POLICY

Our Insider Trading Policy, as adopted by our Board, provides our directors and employees with guidelines for nominationwhen transacting the Company’s securities is appropriate. The Insider Trading Policy prohibits directors and employees from engaging in short sales, options trading, shot-term trading, standing or limit orders, and hedging. In addition, directors and executives with a title of senior vice president or above are prohibited from placing the Company’s securities in margin accounts or otherwise pledging shares of Common Stock. Also, directors and certain employees are required to receive approval from our general counsel’s office before transacting the Company’s securities or establishing contracts, instructions, or plans intended to satisfy the conditions of Rule 10b5-1(c) under the Exchange Act. As of March 30, 2023, all executive officers and directors are in compliance with our Insider Trading Policy.

EXECUTIVE COMPENSATION CLAWBACK POLICY

Our Board has adopted Corporate Governance Guidelines, including an executive compensation clawback policy. The Company’s clawback policy permits recoupment of performance-based or incentive compensation if an executive officer has engaged in fraudulent or other intentional misconduct and the misconduct resulted in a material inaccuracy in the Company’s financial statements or performance metrics that affect such executive officer’s compensation. The Board may seek recoupment of the portion of the executive’s performance-based or incentive compensation paid or awarded to the Board; (3) recommendsexecutive that is greater than would have been paid or awarded if calculated based on the accurate financial statements or performance metrics.

CERTAIN RELATIONSHIPS AND RELATED PARTY TRANSACTIONS

The Board has adopted a Related Person Transaction Policies and Procedures (the “Related Persons Policy”), which provides that all transactions with related persons are subject to approval or ratification by our Audit Committee. With certain exceptions, the Related Persons Policy provides that the Audit Committee shall review the material facts of all transactions with related persons and either approve or disapprove of the transaction. Under the Related Persons Policy, covered transactions include all transactions involving (i) the Company, (ii) amounts in excess of $120,000 and (iii) a Related Person (a term that includes executive officers, directors, nominees for election as directors, beneficial owners of 5% or more of the Company’s outstanding Common Stock and immediate family members of

24

---

Table of Contents

CORPORATE GOVERNANCE MATTERS

the foregoing). The Audit Committee will determine, among other considerations, (i) whether the terms of a covered transaction are fair to the Board structuresCompany and statements of the duties and responsibilities of each committee of the Board; (4) develops and recommendsno less favorable to the BoardCompany than would be generally available absent the relationship with the counterparty, (ii) whether there are business reasons for the transaction, (iii) whether the transaction impairs the independence of an outside director, (iv) whether the transaction would represent an improper conflict of interest and implements corporate governance guidelines applicable(v) whether the transaction is material. If the Company becomes aware of a transaction with a Related Person that has not been approved by the Audit Committee prior to its consummation, the Company; (5) assistsAudit Committee shall review such transaction and evaluate all possible options, including ratification, revision or termination of such transaction and shall take such action as it deems appropriate under the Board in annually reviewing management succession; (6) developscircumstances. The Related Persons Policy is intended to supplement, and monitors an annual processnot supersede, our other policies and procedures with respect to assesstransactions with Related Persons. During the effectiveness ofyear ended December 31, 2022, there were no new transactions with related persons that required the Board and implements and oversees an annual review of the performance of the Board (including evaluations of individual Board members) and each of the Board's standing committees; (7) develops and proposes, for approval by the Board, compensation policies for the Company's non-employee directors; (8) annually reviews contributions to candidates made by the Iron Mountain Incorporated Political Action Committee, or IMPAC, and determines the composition of the IMPAC board; and (9) takes other actions to meet its responsibilities as set forth in its written charter.our Audit Committee.

        Finance Committee.    Although the NYSE listing standards do not require members of the Finance Committee to be independent, all members of the Finance Committee qualify as independent under the NYSE listing standards and the Board's assessment of any material relationships with the Company. The Finance Committee: (1) reviews the Company's capital structure and financial strategies; (2) reviews the Company's material capital allocation decisions, strategic investments and dispositions and other opportunities for maximizing stockholder value; (3) considers and reviews the Company's dividend and share repurchase policies and programs and other strategies to return capital to stockholders; (4) reviews the Company's derivatives and hedging policies and strategies; (5) reviews the Company's investment policies and practices; (6) reviews the Company's credit ratings and strategy, (7) periodically reviews the Company's investor relations strategy, (8) furnishes periodic reports to the Board concerning the Finance Committee's work; and (9) performs such other duties as the Board may assign to the committee from time to time.THE COMPANY’S POLICY AND BOARD OVERSIGHT OF POLITICAL EXPENDITURES

        Risk and Safety Committee.    The Risk and Safety Committee (1) reviews and monitors material safety, security, business continuity, information security and risk management strategies and systems; (2) reviews and monitors material safety, security, business continuity, information security and risk management policies and processes implemented, established and reported on by the Company's

management; (3) monitors the Company's insurance programs; and (4) takes other actions to meet its responsibilities as set forth in its written charter.

Board and Committee Evaluations

        The Nominating and Governance Committee oversees the Board and committee evaluation process. Generally, including in 2015, the Board and each committee conduct self-evaluations by means of written questionnaires completed by each director and committee member. The anonymous responses are summarized and provided to the Board and each committee at their subsequent meetings in order to facilitate an examination and discussion by the Board and each committee of the effectiveness of the Board, committees, individual directors, Board and committee structure and dynamics, and areas for possible improvement. The Nominating and Governance Committee establishes the board and committee evaluation process each year and may determine to use an independent third party evaluation process from time to time in the future.

Risk Oversight

        The Board is responsible for oversight of the Company's management of enterprise risks. Iron Mountain senior management is responsible for the Company's risk management process and the day-to-day supervision and mitigation of enterprise risks. The Board receives regular reports on areas of material Company risk, including strategic, operational, financial, legal and regulatory risks. The Board, or the committee of the Board assigned responsibility for a specific area of risk, receives reports from the Company executive accountable for understanding and mitigating the identified risk. When a committee of the Board receives a risk report, the chairman of such committee provides a summary of the discussion to the Board during the next regularly scheduled Board meeting. This practice allows the Board and each of its committees to remain coordinated in their oversight of enterprise risk. The Risk and Safety Committee provides additional support to the Board in ensuring that the Company's enterprise risk management program is established appropriately and operating effectively.

Political Expenditures

Our Global Political Contribution Policy, adopted by our Nominating and Governance Committee, together with our Code of Ethics and Business Conduct, guide our approach to ethical business behavior and corporate political contributions. Our Global Political Contribution Policy provides that Iron Mountain does not make political contributions in any form or amount from corporate funds or resources, even when permitted by applicable law. This meansIron Mountain does not use corporate funds are not used in support of or opposition to political candidates, political parties, political committees and other political entities organized and operating for political candidates. In addition, corporate funds are not usedcandidates or for "electioneering"“electioneering” communications.

The Company administers IMPAC, which is a non-partisan political action committee supporting congressional candidates at the federal level only. IMPAC is governed by a set of bylaws and supervised by a board of directors composed of senior managers from different areas of the Company. IMPAC allows eligible employees to pool their resources to support candidates who understand the issues important to the Company'sCompany’s business and its employees. Participation in IMPAC is strictly voluntary. Except for administrative expenses, IMPAC is funded solely by the Company'sCompany’s employees and directors and is not supported by funds from the Company. IMPAC complies with federal election laws and all other applicable laws and reports regularly to the Federal ElectionsElection Commission. In addition, IMPAC is governed by a set of bylaws and supervised by a board of directors composed of senior managers from different areas of the Company.

The Company is a member of a number of trade associations that participate in public relations activities such as education and conferences, but not for the purpose of making political contributions. Our Code of Ethics and Business Conduct and our Global Political Contribution Policy are available on our website under the heading "Company/Investors/“Investors/Corporate Governance."

Governance/Governance Documents.”

Stockholder Communications to Board of Directors

        The Board believes it is important to engage effectively with stockholders. To facilitate this engagement, in February 2016, the Board adopted a written Shareholder Engagement and Communication Policy, or the Shareholder Engagement Policy, which outlines the procedures for the Board's engagement and communication with the Company's stockholders. The Shareholder Engagement Policy is overseen by the Nominating and Governance Committee. Under the Shareholder Engagement Policy, any stockholder, security holder or other interested party who desires to communicate with the Board, any individual director, including the Independent Chairman, or the independent or non-management directors as a group, may do so by regular mail or email directed to the Secretary of the Company. Communications to the Board should be mailed to Corporate Secretary, Iron Mountain Incorporated, One Federal Street, Boston, Massachusetts 02110; the Secretary's email address is corporatesecretary@ironmountain.com. Upon receiving such mail or email, the Secretary will assess the appropriate director or directors to receive the message and will forward the mail or email to such director or directors without editing or altering it.

Selection of Board of Directors Nominees

        The Board is responsible for developing and approving criteria, in addition to those set forth in our Corporate Governance Guidelines, for candidates for Board membership. TheOur Nominating and Governance Committee is responsibleannually reviews contributions by the IMPAC, determines the IMPAC board members and reviews the Company’s Political Contribution Policy and the Company’s compliance therewith.

DIRECTOR STOCK OWNERSHIP GUIDELINES

We maintain director stock ownership guidelines that require non-employee directors to achieve and maintain ownership of our Common Stock at or above a prescribed level. Our directors who are also employees of the Company are subject to the Company’s executive stock ownership guidelines described on page 49 of this Proxy Statement. We established these guidelines to help align long-term interests of directors with stockholders. The guidelines require each director to own and retain Common Stock, exclusive of unexercised stock options and performance shares or performance units (“PUs”), having a value equal to six times the director’s annual cash retainer earned for seeking candidates to become Board members, consistentserving on the Board.

As of March 30, 2023, all of the Company’s non-employee directors are in compliance with the criteriadirector stock ownership guidelines.

Each director subject to the Company’s stock ownership guidelines is required to retain an amount equal to 50% of the net shares received as a result of the settlement or vesting of restricted stock, restricted stock units (“RSUs”), PUs or the exercise of stock options until such director meets the minimum ownership threshold. “Net shares” are those shares that remain after shares are sold or netted to pay any applicable taxes or purchase price. Because directors must retain a percentage of shares resulting from the vesting of RSUs until they achieve the minimum share ownership threshold, there is no minimum time period required to comply initially with the guidelines.

Table of Contents

CORPORATE GOVERNANCE MATTERS

DIRECTOR COMPENSATION

2022 DIRECTOR COMPENSATION PLAN AND DIRECTOR DEFERRED COMPENSATION PLAN

Directors who are employees of the Company do not receive additional compensation for serving on the Board. Pursuant to the 2022 Company’s Compensation Plan for Non-Employee Directors, non-employee directors received an annual retainer of $80,000 in 2022, and committee members and committee chairs received annual retainer fees as set forth in the Corporate Governance Guidelines and approved by the Board, and for recommending candidates to the entire Board for selection by the Board for nomination to fill vacanciesbelow:

Any non-employee director who served on the Board or expiring terms of directors at each annual meeting of stockholders. The Board as a whole is responsiblecommittee for nominating individuals for election toless than the Board byentire year received a pro rated retainer based on the stockholders and for filling vacanciesdates such non-employee director served on the Board that may occur betweenor the applicable committee. In addition, our Chair receives a retainer of $150,000.

Non-employee directors received annual meetingsgrants of RSUs for the stockholders.

        Nominees for director will be selected on the basisnumber of their integrity, experience, achievements, judgment, intelligence, personal character, ability to make independent analytical inquiries, willingness to devote adequate time to Board duties and likelihood that they will be able to serve on the Board for a sustained period. In connection with the selection of nominees for director, the Board's policy is to give due consideration to the Board's overall balance of diversity of perspectives, backgrounds and experiences. To implement and review the effectivenessshares of our diversity policy,Common Stock equal to $170,000 divided by the Nominating and Governance Committee reviews the appropriate skills and characteristics of members of the BoardFair Market Value (as defined in the context of the then current composition of the Board. It is the practice of the Nominating and Governance Committee to then consider these factors when screening and evaluating candidates for nomination or re-election to the Board. The Board will not nominate for election as director any candidate who has not agreed to tender, promptly following the annual meeting at which he or she is elected as director, an irrevocable resignation that will be effective upon (1) the failure to receive the required number of votes for re-election at the next annual meeting of stockholders at which he or she faces re-election, and (2) acceptance of such resignation by the Board.

        The Nominating and Governance Committee will consider, as part of the process for identifying individuals who might be candidates, individuals who are properly recommended by stockholders for nomination by the Board at a meeting of stockholders at which directors are to be elected. To be proper, a recommendation for a nominee for director with respect to a meeting of stockholders must comply with applicable law, the Company's Bylaws and the Company's Corporate Governance Guidelines. The Nominating and Governance Committee will consider any suggestions offered by other directors or stockholders with respect to potential directors, and there will be no difference in the manner in which potential nominees are evaluated. However, the Nominating and Governance Committee and the Board are not required to enlarge the size of the Board in order to nominate an otherwise fully qualified candidate proposed by a stockholder. A stockholder wishing to nominate a

director directly must comply with the procedures described in the Company's Bylaws and this Proxy Statement.

        In 2015 the Nominating and Governance Committee did not retain the services of, and did not pay a fee to, any third party to identify or assist in identifying or evaluating potential nominees to our Board.

Nominations and Proposals of Stockholders

        A stockholder who, in accordance with Rule 14a-8, or Rule 14a-8, under the Securities Exchange Act of 1934, as amended, or the Exchange Act, wants to present a proposal for inclusion in the Company's 2017 Proxy Statement and proxy card relating to the 2017 Annual Meeting of Stockholders must submit the proposal by December 28, 2016. In order for the proposal to be included in the Proxy Statement, the stockholder submitting the proposal must meet certain eligibility standards and comply with certain regulations established by the SEC.

        Stockholders who wish to present a business proposal or nominate persons for election as directors at the Company's 2017 Annual Meeting of Stockholders must provide a notice of the business proposal or nomination in accordance with Section 2.4 of our Bylaws, in the case of business proposals, or Section 3.2 of our Bylaws, in the case of director nominations. In order to be properly brought before the 2017 Annual Meeting of Stockholders, Sections 2.4 and 3.2 of our Bylaws require that a notice of the business proposal the stockholder wishes to present (other than a matter brought pursuant to Rule 14a-8), or the person or persons the stockholder wishes to nominate as a director, must be received at our principal executive office not less than 90 days, and not more than 120 days, prior to the first anniversary of the Company's prior year's annual meeting. Therefore, any notice intended to be given by a stockholder with respect to the Company's 2017 Annual Meeting of Stockholders pursuant to our Bylaws must be received at our principal executive office no earlier than February 17, 2017 and no later than March 19, 2017. However, if2014 Plan) on May 10, 2022, the date of our 20172022 Annual Meeting of Stockholders occurs more than 30 days before or 30 days after June 17, 2017, the anniversary of the 2016 Annual Meeting of Stockholders, a stockholder notice will be timely if it is received at our principal executive office by the later of (1) the 120^th day prior to such annual meeting or (2) the close of businessStockholders. The RSUs vested immediately on the tenth day following the day on which public disclosure of the date of grant.

The Director Deferred Compensation Plan (the “DDCP”) allows non-employee directors to defer the meeting was made. Toreceipt of between 5% and 100% of their cash retainers, in which case participating non-employee directors receive shares of phantom stock in an amount equal to the amount of the cash retainer deferred divided by the fair market value of one share of Common Stock as of the crediting date. Non-employee directors may also defer some or all of their annual RSU grant under the DDCP and receive a number of shares of phantom stock equal to the amount of the annual RSU grant. Dividends, if any, accrued on such phantom stock are deemed to be similarly deferred and credited to the participating non-employee director’s account. The shares of phantom stock are payable in propershares of Common Stock on various dates selected by each participating non-employee director or as otherwise provided in the DDCP. Deferral elections and elections relating to the timing and form a stockholder's notice must includeof payments are made prior to the specifiedperiod in which the retainers, fees and awards are earned. The Company does not contribute any matching, profit sharing or other funds to the DDCP for any participating director. Amounts under the DDCP are treated as invested in shares of our Common Stock. The DDCP is administered by the Chair of the Compensation Committee and the executive vice president primarily responsible for oversight and administration of our compensation programs.

26

The Compensation Committee annually reviews, with assistance from our independent compensation consultants, the business proposal or nominee, as described in Sections 2.4, 3.2 and 3.3compensation of our Bylaws.

        All proposals must be mailednon-employee directors in comparison to companies with similar revenues and business and makes adjustments it believes are appropriate. Based on this review, the Compensation Committee did not recommend any change to the Company's principal executive office, at the address stated herein, and should be directed to the attentioncompensation of the Secretaryour non-employee directors for 2023.

Table of the Company.Contents

Code of EthicsCORPORATE GOVERNANCE MATTERS

OTHER CORPORATE GOVERNANCE MATTERS

CODE OF ETHICS

Our Code of Ethics and Business Conduct applies to each of the Company'sCompany’s employees, including officers and directors. Our Code of Ethics and Business Conduct is posted on our website, www.ironmountain.com, under the heading "Company/Investors/“Investors/Corporate Governance."Governance/ Governance Documents.” A printed copy of our Code of Ethics and Business Conduct is also available free of charge to any stockholder who requests a copy. We intend to disclose any amendment to, or waiver from, a provision of our Code of Ethics and Business Conduct applicable to our CEO, chief financial officer or principal accounting officer or controller by posting such information on our website. Any waivers applicable to any other executive officers will also be promptly disclosed to stockholders on our website.

ITEM 2

ADVISORY VOTE ON THE COMPENSATION OF SUSTAINABILITY

OUR NAMED APPROACH

Iron Mountain is committed to living by our values and putting them into action every day and in everything we do – from safeguarding our customers’ information to empowering employees, serving our communities, and protecting the environment. Our ESG principles are integrated across the business and we strive to be our customers’ most trusted partner for protecting and unlocking the value of what matters most to them in innovative and socially responsible ways.

We conduct periodic materiality assessments, which serve to prioritize ESG topics through engagement with internal and external stakeholders. This process helps to manage ESG risks and identify the topics that are most relevant to the success of our company. While our priority issues evolve, we remain focused on three core areas that will not only protect and elevate the power of our customers’ work, but enable a lasting, positive impact on people, planet and performance.

We are committed to transparent reporting on our ESG initiatives and other sustainability efforts, and we publish an annual report in accordance with the guidelines set out by the Task Force for Climate Related Financial Disclosures and the Global Reporting Initiative Standards. A copy of our corporate responsibility report is available on the “About Us” section of our website, www.ironmountain.com, under the heading “Sustainability”.

OUR PLANET

We are committed to reducing our impact on the environment while driving value to our customers, investors and the communities in which we operate.

OUR PEOPLE

Attracting, developing, and empowering individuals with a wide range of experiences, capabilities, and points of view are key components of our success.

OUR COMMUNITIES

We engage with our local communities and support charitable causes.

28

EXECUTIVE OFFICERS
COMPENSATION

In accordance with the requirements of Section 14A of the Exchange Act and related rules of the SEC, we are including this separate proposal subject to stockholder votefor stockholders to approve, on a non-binding, advisory basis, the compensation of our Named Executive Officersnamed executive officers listed in the "SummarySummary Compensation Table"Table appearing inon page 52 of this Proxy Statement as disclosed in this Proxy Statement pursuant to Item 402 of Regulation S-K.(collectively, our “Named Executive Officers” or our “NEOs”).

Our executive compensation is designed to reward executive performance that contributes to ourthe long-term success while encouraging behavior that is in ourof the Company and our stockholders' long-term best interests. We also seekstockholders and to attract, motivate, reward and retain the senior management talent required to achieve our corporate objectives and increase stockholder value. At the core of our executive compensation programs is our "pay“pay for performance"performance” philosophy that links competitive levels of executive compensation to achievements of our overall strategy and business goals, as well asincluding predetermined objectives. We believe our compensation program is strongly aligned with the interests of our stockholders and sound corporate governance principles. We urge you to read the "Compensation“Compensation Discussion and Analysis"Analysis” section of this Proxy Statement and the compensation tables and the other narrative discussioncompensation disclosures contained in this Proxy Statement for additional details on our executive compensation, including our compensation philosophy and objectives and the compensation of our Named Executive Officers.NEOs.

The vote on this proposal is not intended to address any specific element of compensation; rather, the vote relates to the overall compensation of our Named Executive Officers,NEOs, as described in this Proxy Statement in accordance with the compensation disclosure rules of the SEC. To the extent there is any significant vote against the compensation paid to the Named Executive OfficersNEOs as disclosed in this Proxy Statement, the Compensation Committee will evaluate whether any actions are necessary to address the concerns of stockholders.

We believe the compensation paid to our NEOs for fiscal 2022 appropriately reflects and rewards our executive officers’ contributions to the performance of Iron Mountain and is aligned with the long-term interests of our stockholders. In deciding how to vote on this proposal, stockholders are encouraged to read the “Compensation Discussion and Analysis” and “Executive Compensation” sections of this Proxy Statement.

Based on the above, we request that you indicate your support for our executive compensation philosophy and practices by voting to approve, on a non-binding, advisory basis, the following resolution:

        "RESOLVED,“RESOLVED, that the compensation paid to the Company'sCompany’s Named Executive Officers, as disclosed pursuant to Item 402 of Regulation S-K, including the Compensation Discussion and Analysis, compensation tables and narrative discussion in the Proxy Statement for the 20162023 Annual Meeting of Stockholders, is hereby APPROVED."”

Required Vote

REQUIRED VOTE The affirmative vote of a majority of the votes properly cast at the Annual Meeting is required to approve the non-binding advisory vote on the compensation of our NEOs, as described in the “Compensation Discussion and Analysis” section of this Proxy Statement and the compensation tables and the other narrative compensation disclosures contained in this Proxy Statement. For the purposes of determining the number of votes cast, only those cast “For” or “Against” are included. The opportunity to vote on this resolution is required pursuant to Section 14A of the Exchange Act. However, as an advisory vote, the vote on this resolution is not binding upon the Company and serves only as a recommendation to the Board. Nonetheless, the Compensation Committee, which is responsible for designing and administering our executive compensation programs, and the Board value the opinions expressed by stockholders and will consider the outcome of the vote when making future executive compensation decisions. Our current policy is to provide stockholders with an opportunity to approve executive compensation each year at our annual meeting of stockholders. We currently expect that the next such vote will occur at our 2024 Annual Meeting of Stockholders.

2022 PROXY STATEMENT	29

Table of Contents

EXECUTIVE COMPENSATION

COMPENSATION DISCUSSION AND ANALYSIS

EXECUTIVE SUMMARY

OVERVIEW

We help organizations around the world protect their information, reduce storage costs, comply with regulations, facilitate corporate disaster recovery, and better use their information and information technology (“IT”) infrastructure for business advantages, regardless of its format, location or life cycle stage. We achieve this by storing physical records and data backup media, offering information management solutions, and providing data center space for enterprise-class colocation and hyperscale deployments. We offer comprehensive records and information management services and data management services, along with the expertise and experience to address complex storage and information management challenges such as rising storage rental costs, legal and regulatory compliance, and disaster recovery requirements. We provide secure and reliable data center facilities to protect digital information and ensure the continued operation of our Named Executive Officers, as described in the "Compensation Discussioncustomers’ IT infrastructure, with reliable and Analysis" section, the compensation tables and the other narrative compensation disclosures contained in this Proxy Statement. For the purpose of determining whether a majority of the votes has been cast in favor of the approval of this resolution, only those cast "For" or "Against" are included, and any abstentions or broker non-votes will not count in making that determination. The opportunity to vote on this resolution is required pursuant to Section 14A of the Exchange Act. However, as an advisory vote, the vote on this resolution is not binding upon the Company and serves only as a recommendation to our Board. Nonetheless, the Compensation Committee, which is responsible for designing and administering our executive compensation programs, and the Board value the opinions expressed by stockholders and will consider the outcome of the vote when making future compensation decisions for our Named Executive Officers.

flexible deployment options. Our current policy isasset lifecycle management (“ALM”) business allows us to provide stockholders withend-to-end asset lifecycle services for hyperscale, corporate data center and corporate end-user device assets.

Founded in an opportunity to approve the compensation paid to our Named Executive Officers each year at our annual meeting of stockholders. We currently expect that the next such vote will occur at our 2017 Annual Meeting of Stockholders.

The Board recommends that you vote FOR the approval of the foregoing non-binding, advisory resolution approving the compensation of our Named Executive Officers.

ITEM 3

RATIFICATION OF THE SELECTION OF
INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

        Subject to ratification by the stockholders, the Audit Committee has selected the firm of Deloitte & Touche LLP as the Company's independent registered public accounting firm for the current year.

        Representatives of Deloitte & Touche LLP are expected to be present at the Annual Meeting. They will have the opportunity to make a statement if they desire to do so and will be available to respond to appropriate questions from stockholders who are present at the Annual Meeting.

        The feesunderground facility near Hudson, New York in 1951, we paid to Deloitte & Touche LLP in 2015 are shown in the table appearing on page 75 of this Proxy Statement.

        If the stockholders do not ratify the selection of Deloitte & Touche LLP as the Company's independent registered public accounting firm, the selection of accountants will be reconsidered by the Audit Committee.

Required Vote

        The affirmative vote of holders of a majority of the votes properly cast at the Annual Meeting is required to ratify the selection of Deloitte & Touche LLP to serve as the Company's independent registered public accounting firm for the current fiscal year. For purposes of determining the number of votes cast, only those cast "For" or "Against" are included, and any abstentions will not count in making that determination.

The Board recommends that you vote FOR the ratification of the selection of Deloitte & Touche LLP.

SECURITY OWNERSHIP OF CERTAIN BENEFICIAL OWNERS AND MANAGEMENT

        The following table sets forth certain information known to the Company with respect to beneficial ownership of Common Stock by: (1) each director and nominee for director; (2) the Named Executive Officers; (3) all directors and executive officers of the Company as a group; and (4) each stockholder known by us to be the beneficial owner ofhad more than 5% of the Common Stock. Such information is presented as of March 31, 2016, except as otherwise noted.

Equity Compensation Plan Information

        The following provides certain equity compensation plan information with respect to all of our equity compensation plans in effect as of December 31, 2015:

EXECUTIVE COMPENSATION
COMPENSATION DISCUSSION AND ANALYSIS

Executive Summary

        The primary objectives of our compensation programs are to reward the achievement of both Company and individual goals and to align the interests of our executives with the creation of stockholder value. In keeping with these objectives, our compensation programs are designed to align with the objectives of our strategic plan developed by senior leadership, or the Strategic Plan, and reward teamwork and contribution to the successful achievement of our enterprise goals and financial objectives.

2015 Developments

•

Reaffirmed our Strategic Plan, which is focused on three core pillars for growth—Developed Markets⁽¹⁾, Emerging Markets⁽²⁾ and Adjacent Businesses⁽³⁾; extended our financial outlook to 2020 at our Investor Day in October 2015; and embarked on a multi-year transformation program, or the Transformation Program, intended to improve operational efficiency and provide additional investment for growth



•

Entered into agreement to acquire Recall, which is expected to deliver meaningful synergies and earnings accretion once completed



•

Achieved operational performance generally in line with expectations, measured in constant currency; however, the strengthening of the U.S. dollar negatively impacted our reported results



•

Continued to deliver rewards through our pay-for-performance model that balances short-term operational performance and the creation of long-term stockholder value:



•

our executives were rewarded for 2015 operational performance through our short-term incentive program



•

the value of our executives' long-term incentives, the largest portion of their compensation, declined significantly due to the decline in our share price during 2015 and the impact of the strengthening U.S. dollar on the performance of certain of our Performance Units, or PUs, which are measured on a reported basis (i.e., including the impact of currency fluctuation)

Strategic Plan

        During 2015, we continued to make progress executing on the Strategic Plan, which includes (i) three core growth and value pillars that drive our business strategy to generate more income from developed markets and higher growth markets and businesses and (ii) enabling activities that are designed to improve efficiency and leverage scale to support the investment and execution of the three

⁽¹⁾

"Developed Markets" include United States, Canada, western Europe and Australia.

⁽²⁾

"Emerging Markets" include central and eastern Europe, Latin America and the Asia Pacific region (excluding Australia).

⁽³⁾

"Adjacent Businesses" primarily include our data center and fine art storage businesses.

core pillars and maintain and strengthen our dividend. The Strategic Plan's growth and value pillars, as well as the enabling activities, are represented in the following graphic:

        The table below highlights the significant 2015 achievements with respect to each core growth and value pillar of our Strategic Plan:

Aligning Program Design with the Strategic PlanCOMPENSATION PHILOSOPHY AND PRACTICES