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EXECUTIVE COMPENSATION

PROPOSAL 2	APPROVAL, BY A NON-BINDING ADVISORY VOTE, OF AN AMENDMENT TO THE 2014 PLAN COMPENSATION OF OUR NAMED EXECUTIVE OFFICERS
		The Board recommends that you vote FORthe approval of an amendment to the 2014 Plan to increasenon-binding, advisory resolution approving the numbercompensation of shares of Common Stock authorized for issuance by 8,000,000, from 12,750,000 to 20,750,000, to extend the termination date of the 2014 Plan from May 24, 2027 to May 12, 2031, to provide that, other than in certain circumstances, no equity-based award will vest before the first anniversary of the date of grant and to provide that dividends and dividend equivalents are not paid with respect to stock options or stock appreciation rights.our Named Executive Officers.

In accordance with the requirements of Section 14A of the Exchange Act and related rules of the SEC, we are including this separate proposal for stockholders to approve, on a non-binding, advisory basis, the compensation of our named executive officers listed in the Summary Compensation Table appearing on page 52 of this Proxy Statement (collectively, our “Named Executive Officers” or our “NEOs”).

The Board has unanimously approved, and unanimously recommendsOur executive compensation is designed to reward performance that the stockholderscontributes to long-term success of the Company approve, an amendment, attached hereto as Appendix A (the “Amendment”),and our stockholders and to attract, motivate, 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 for performance” philosophy that links competitive levels of executive compensation to achievements of our overall strategy and business goals, including 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 Discussion and Analysis” section of this Proxy Statement and the compensation tables and the other narrative compensation disclosures contained in this Proxy Statement for additional details on our executive compensation, including our compensation philosophy and objectives and the compensation of our NEOs.

The vote on this proposal is not intended to address any specific element of compensation; rather, the vote relates to the 2014 Plan to increaseoverall compensation of our NEOs, as described in this Proxy Statement in accordance with the number of shares of Common Stock authorized for issuance under the 2014 Plan by 8,000,000 from 12,750,000 to 20,750,000, to extend the termination datecompensation disclosure rules of the 2014 Plan from May 24, 2027SEC. To the extent there is any significant vote against the compensation paid to May 12, 2031, to provide that, other than in certain circumstances described in the Amendment and laterNEOs as disclosed in this Proposal 2, no equity-based award shall vest, in whole or in part, beforeProxy Statement, the first anniversaryCompensation Committee will evaluate whether any actions are necessary to address the concerns of stockholders.

We believe the datecompensation paid to our NEOs for fiscal 2021 appropriately reflects and rewards our executive officers’ contributions to the performance of grant or, inIron Mountain and is aligned with the caselong-term interests of vesting based uponour stockholders. In deciding how to vote on this proposal, stockholders are encouraged to read the attainment“Compensation Discussion and Analysis” and “Executive Compensation” sections of performance goals or other performance-based objectives,this Proxy Statement.

Based on the first anniversary ofabove, 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 commencement offollowing resolution:

“RESOLVED, that the period over which performance is evaluated, and to provide that dividends and dividend equivalents shall not becompensation paid with respect to a stock option or stock appreciation right.

The Board believes that equity interests are a significant factor in the Company’s ability to attract, retain and motivate key employees, directors and other service providers (generally, and in connection with acquisitions) that are critical to the Company’s long-term successNamed Executive Officers, as disclosed pursuant to Item 402 of Regulation S-K, including the Compensation Discussion and that an increaseAnalysis, compensation tables and narrative discussion in the numberProxy Statement for the 2022 Annual Meeting of shares available for issuance under the 2014 PlanStockholders, is necessary in order to provide those persons with incentives to serve the Company.

hereby APPROVED.”

2014 PLAN

FACTORS FOR SHARE INCREASE

In approving the increase in the number of shares reserved for issuance under the 2014 Plan, the Board considered the following factors:

EQUITY RUN RATE

As of March 1, 2021, only 955,587 total shares remained available for grant under the Company’s equity plans, all of which are available under the 2014 Plan. As of March 1, 2021, there are no shares remaining available for grant under the Iron Mountain Incorporated 2002 Stock Incentive Plan. The Board currently believes that the proposed increase of 8,000,000 shares under the 2014 Plan should result in an adequate number of shares of Common Stock for future awards for approximately three (3) years, although this forecast includes several assumptions and there are a number of factors that could impact the Company’s future equity share usage. Among the factors that will impact the Company’s share usage are: changes in market grant values; changes in the number of recipients; changes in the Company’s stock price; payout levels of performance-based awards; changes in the structure of the Company’s long-term incentive programs; and forfeitures of outstanding awards.

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OVERHANG

If stockholders approve the increase in the reserve under the 2014 Plan, the total shares available for grant under all of the Company’s equity plans would be 8,955,587 and would represent approximately 3.1% of 288,704,904 shares of Common Stock outstanding as of March 1, 2021.

As of March 1, 2021, the Company had approximately 3,100,186 full value awards outstanding under all of its equity plans. In addition, as of March 1, 2021, the Company had approximately 5,065,733 stock options outstanding under all of its equity plans, which stock options had a weighted average exercise price of $35.83 and a weighted average remaining term of 6.35 years. If stockholders approve the Amendment, as of March 1, 2021, the potential overhang⁽¹⁾ from all stock awards granted and available to employees and directors would increase from 3.06% to 5.60%.

As a result of increasing the number of shares, it is also possible to extend the termination date of the 2014 Plan, which the Board believes is an appropriate action.

In addition, the Amendment will provide that equity-based awards generally shall not vest, in whole or in part, before the first anniversary of the date of grant or, in the case of vesting based upon the attainment of performance goals or other performance-based objectives, the first anniversary of the commencement of the period over which performance is evaluated. The Compensation Committee may make exceptions for accelerated vesting in connection with death, disability or retirement, awards of an acquired, consolidated or merged entity that are substituted for Awards (as defined below) that do not reduce the vesting period of the award being replaced, or for equity-based awards that result in the issuance of an aggregate of up to 5% of the shares available for grant under the 2014 Plan. In addition, unvested equity-based awards will also undergo accelerated vesting upon certain involuntary terminations in connection with a change in control (as discussed below). The Board believes that providing a 12-month minimum vesting period on all equity-based awards granted under the 2014 Plan is consistent with the principles of good corporate governance and will promote the interests of stockholders and is advisable. For these same reasons, the Amendment will also provide that dividends and dividend equivalents shall not be paid with respect to a stock option or stock appreciation right.

The closing price of the Company’s Common Stock on March 1, 2021 was $34.73.

SUMMARY OF THE 2014 PLAN

The following summary of the material features of the 2014 Plan is qualified in its entirety by reference to the complete text of the 2014 Plan, which is filed as an appendix to the Company’s Proxy Statements on Schedule 14A filed on December 23, 2014, as amended by the First Amendment to the Iron Mountain Incorporated 2014 Stock and Cash Incentive Plan, filed as Exhibit 10.1 to the Company’s Form 8-K, dated May 23, 2017, and the Second Amendment to the Iron Mountain Incorporated 2014 Stock and Cash Incentive Plan, filed as Exhibit 10.01 to the Company’s Form 10-Q for the quarter ended September 30, 2018.

The 2014 Plan permits the issuance of equity-based awards, including incentive stock options (“ISOs”), nonqualified stock options (“NSOs”), grants of Common Stock, whether or not subject to restrictions, stock appreciation rights (“SARs”), RSUs and PUs, that vest based on certain performance criteria, and cash-based awards that may be earned based on certain performance criteria (collectively, “Awards”). The 2014 Plan initially reserved 7,750,000 shares of Common Stock, which was subsequently increased to 12,750,000 by an amendment that was adopted by resolution of the Board on March 24, 2017. If stockholders approve the Amendment, the total amount of Common Stock authorized for issuance under the 2014 Plan will be 20,750,000.

EFFECTIVE DATE AND DURATION

The 2014 Plan became effective on January 20, 2015. The 2014 Plan currently provides for termination on May 24, 2027 or May 12, 2031 if the Amendment is adopted, unless earlier terminated by the Board. Termination of the 2014 Plan will not affect Awards made prior to termination, but no new Awards will be made after the 2014 Plan terminates.

PURPOSE AND ELIGIBILITY

The purpose of the 2014 Plan is to advance the interests of our stockholders by enhancing our ability to attract, retain and motivate persons who are expected to make important contributions to us and our affiliates, and to provide those persons with equity ownership opportunities and performance-based equity and cash compensation. For this purpose, any present or future parent or subsidiary corporation, and any other present or future business venture in which we have a controlling interest, may be treated as an affiliate of ours.

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The persons eligible to receive Awards are our and our affiliates’ employees, officers, directors, consultants and advisors and those of our affiliates. The recipient of an Award under the 2014 Plan is referred to below as a “Participant.” At this time, we consider approximately 1,500 persons eligible to receive Awards pursuant to the 2014 Plan.

ADMINISTRATION

Although our Board has the authority to administer the 2014 Plan, it has generally delegated this authority to the Compensation Committee, which administers all of our equity-based compensation plans. Each member of the Compensation Committee is a “non-employee director” within the meaning of Rule 16b-3 promulgated under the Exchange Act and qualifies as independent under NYSE listing standards.

Subject to the terms of the 2014 Plan, the Compensation Committee has the authority to: (1) select or approve Award recipients; (2) determine the terms and conditions of Awards, including the price to be paid for any Common Stock; and (3) interpret the 2014 Plan and prescribe rules and regulations for its administration.

Awards, at the discretion of the Compensation Committee, may be transferable to members of a Participant’s immediate family or to a family partnership or trust for the benefit of a Participant’s immediate family.

SHARES SUBJECT TO THE 2014 PLAN

The total number of shares of our Common Stock that may be subject to Awards under the 2014 Plan may not exceed 12,750,000 shares, or 20,750,000 shares if the Amendment is approved. The shares may be authorized but unissued shares or treasury shares. The total amount of Common Stock that may be granted under the 2014 Plan to any single person in any year may not exceed in the aggregate 1,250,000 shares. The aggregate economic value of all equity-based and equity-related Awards granted under the 2014 Plan in any year to any director who is not an employee of the Company shall not exceed $500,000, determined, for each Award, by using the Fair Market Value (as defined in 2014 Plan) as of the date such Award is granted. In the event a cash-based Award under the 2014 Plan is made, such Award shall not exceed $7,500,000 in any year to any single person.

To the extent that an option or other form of Award lapses or is forfeited, the shares subject to the Award will again become available for grant under the terms of the 2014 Plan.

As of March 1, 2021, 6,025,107 equity-based Awards were outstanding under the 2014 plan, consisting primarily of stock options, target PUs and RSUs.

STOCK OPTIONS

The Compensation Committee may grant ISOs and NSOs (each as defined in the 2014 Plan) under the 2014 Plan. The Compensation Committee determines the number of shares of Common Stock subject to each option, its exercise price, its duration and the manner and time of exercise; provided, however, that no option may be issued under the 2014 Plan with an exercise price that is less than the Fair Market Value of our Common Stock as of the date the option is granted, no option will have a duration that exceeds ten years, and, if the Amendment is approved, dividends and dividend equivalents shall not be paid with respect to an option. ISOs may be issued only to employees of the Company or a corporate subsidiary thereof and, in the case of a more than ten percent stockholder, must have an exercise price that is at least 110% of the Fair Market Value of our Common Stock as of the date the option is granted, and may not have a duration of more than five years.

The Compensation Committee, in its discretion, may provide that any option is subject to vesting limitations that make it exercisable during its entire duration or during any lesser period of time.

The exercise price of an option may be paid in cash, by delivery of a recourse promissory note secured by the Common Stock acquired upon exercise of the option (except that such a loan would not be available to any of our executive officers or directors), by means of a “cashless exercise” procedure in which a broker transmits to us the exercise price in cash, either as a margin loan or against the Participant’s notice of exercise and confirmation by us that we will issue and deliver to the broker stock certificates for that number of shares of Common Stock having an aggregate Fair Market Value equal to the exercise price, or agrees to pay the exercise price to us in cash upon our receipt of stock certificates, by delivery of shares of Common Stock owned by the Participant, by a “net exercise” in the case of an NSO or by any combination of the methods listed.

2021 PROXY STATEMENT30	33

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EXECUTIVE COMPENSATION

COMPENSATION DISCUSSION AND ANALYSIS

CORPORATE GOVERNANCE MATTERS

Except in connection with a corporate transaction involving the Company, the terms of an option may not be amended to reduce the exercise price (or cancel the option for cash, other Awards or other options with an exercise price less than the exercise price of the existing option) without stockholder approval.

STOCK APPRECIATION RIGHTS

The Compensation Committee may also grant SARs to Participants on such terms and conditions as it may determine. SARs may be granted separately or in connection with an option. No SAR may be issued under the 2014 Plan with an exercise price that is less than the Fair Market Value of our Common Stock as of the date the SAR is granted, and no SAR will have a duration that exceeds ten years. If the Amendment is approved, dividends and dividend equivalents shall not be paid with respect to a SAR. Upon the exercise of a SAR, the Participant is entitled to receive payment equal to the excess of the Fair Market Value, on the date of exercise, of the number of shares of Common Stock for which the SAR is exercised over the exercise price for the Common Stock under a related option or, if there is not a related option, over an amount per share stated in the agreement setting forth the terms and conditions of the SAR.

Payment to the Participant may be made in cash or other property, including Common Stock, in accordance with the provisions of the SAR agreement.

Except in connection with a corporate transaction involving the Company, the terms of a SAR may not be amended to reduce the exercise price (or cancel a SAR for cash, other Awards or other SARs with an exercise price less than the exercise price of the existing SAR) without stockholder approval.

STOCK GRANTS

The Compensation Committee may make an Award in the form of one or more of the following forms of stock grant. Stock grants (including RSUs and PUs at settlement) generally will provide the Participant with all of the rights of a stockholder, including the right to vote and to receive payment of dividends.

STOCK GRANT WITHOUT RESTRICTION

The Compensation Committee may make a stock grant without any restrictions.

RESTRICTED STOCK AND RESTRICTED STOCK UNITS

The Compensation Committee may issue shares of Common Stock to a Participant with restrictions determined by the Compensation Committee in its discretion. Restrictions could include conditions that require the Participant to forfeit the shares in the event that the Participant ceases to provide services to us or any of our affiliates thereof before a stated time.

RSUs are similar to restricted stock except that no shares are actually issued to the Participant on the RSU grant date. Rather, and provided all applicable restrictions are satisfied, shares of Common Stock are generally delivered at settlement of the Award. The period of restriction, the number of shares of restricted stock or the number of RSUs granted, the purchase price, if any, and such other conditions and/or restrictions as the Compensation Committee may establish will be set forth in an Award agreement.

Participants holding RSUs will not have voting rights or other rights as a stockholder until any shares related to the RSU are issued. After all conditions and restrictions applicable to restricted shares and/or RSUs have been satisfied or have lapsed, shares of restricted stock will become freely transferable and RSUs may be settled in cash, in shares of our Common Stock, or in some combination of cash and shares of our Common Stock, as determined by the Compensation Committee and stated in the Award agreement.

PERFORMANCE SHARES AND PERFORMANCE UNITS

With respect to an Award of performance shares and/or PUs, the Compensation Committee will establish performance periods and performance goals. The extent to which a Participant achieves his or her performance goals during the applicable performance period will determine the value and/or the number of performance shares and/or PUs earned by such Participant. Payment of earned performance shares and/or PUs will be in cash, shares of our Common Stock, or some combination of cash and shares of our Common Stock, as determined by the Compensation Committee and stated in the Award agreement.

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DIVIDENDS

Participants holding restricted stock and performance shares will be entitled to receive dividends on our shares, provided that in the discretion of the Compensation Committee Participants will not be entitled to dividends with respect to unvested restricted stock and performance shares until the stock or shares vest, respectively. Dividend equivalent units may, but are not required to, be issued with respect to RSUs or PUs and may be paid in cash, additional shares of our Common Stock, or a combination on the date the shares are delivered, all as determined by the Compensation Committee and stated in the Award agreement.

CASH-BASED AWARDS

The Compensation Committee may make a cash-based Award in an amount and upon such terms as the Compensation Committee may determine, based on the achievement of performance goals established by the Compensation Committee.

PERFORMANCE GOALS

Prior to the Tax Cuts and Jobs Act of 2017 (“TCJA”) eliminating the performance-based compensation exemption, if the Compensation Committee made an Award intended to qualify as “performance-based compensation” under Section 162(m) of the Code as then in effect (including a PU or a cash-based Award), the performance goals selected by the Compensation Committee needed to be based on the achievement of specified levels of one, or any combination, of the following business criteria, measured in the aggregate or on a per share basis (if appropriate): EBITDA (earnings before interest, taxes, depreciation and amortization); OIBDA (operating income before depreciation and amortization); adjusted OIBDA or Contribution (as defined in the 2014 Plan); gross revenues; storage rental revenue; growth rate; capital spending; capital efficiency; maintenance capital spending; free cash flow; funds from operations (as defined by the National Association of Real Estate Investment Trusts); funds from operations (normalized); adjusted funds from operations; building utilization; racking utilization; dividends; same store sales; same store net operating income; operating income (before or after taxes); net operating income; attaining budget; return on total or incremental invested capital; gross profit or margin; operating profit or margin; net earnings (before or after taxes); earnings per share; adjusted earnings per share; net income; share price (including but not limited to growth measures and total stockholder return); return on assets, return on equity, return on sales or return on revenue; other cash flow measures (including operating cash flow, cash flow return on equity, cash flow return on investment and free cash flow before acquisitions and discretionary investments); productivity ratios or metrics; market share; customer satisfaction; working capital targets; storage volume; organizational or transformational metrics; and achievement of stated corporate goals including, but not limited to acquisitions or dispositions, alliances, joint ventures, international development, and internal expansion. Although the 2014 Plan continues to provide the foregoing business criteria as possible performance-based metrics for an Award, the TCJA’s elimination of the performance-based compensation exemption under Section 162(m) of the Code may cause certain of our compensation arrangements to result in non-deductible compensation when the total exceeds $1,000,000 (other than certain historical awards that meet transition rules for continued deductibility under the TCJA).

Any such criteria, whether alone or in combination, may be applied on the basis of our and/or our affiliates as a whole or on any business unit or subset of us and/or an affiliate of ours and may be measured directly, as a growth rate or by comparing the result to the performance of a group of competitor companies, a published or special index determined by the Compensation Committee or other benchmarks determined by the Compensation Committee. The objectives shall be further adjusted by the Compensation Committee as necessary to eliminate the effect on the stated performance goals of unplanned acquisitions or dispositions, changes in foreign exchange rates, discrete tax items identified by the Compensation Committee, changes in accounting standards, variances to planned annual incentive compensation expense and expenses associated with unusual or extraordinary items that could not be reasonably anticipated, as long as those items or changes are material to the performance measure.

After the close of the applicable performance period, which may consist of more than one year, and generally before the close of the next year’s first quarter, the Compensation Committee will determine the extent to which the performance goals were satisfied and make a final determination with respect to an Award.

In the event that applicable tax laws change to permit Compensation Committee discretion to alter the performance goals without obtaining stockholder approval, the Compensation Committee will have sole discretion to make any such alterations.

EFFECT OF CERTAIN CORPORATE TRANSACTIONS

In the event of a stock split, reverse stock split, stock dividend, recapitalization, combination of shares, reclassification of shares, spin-off or other similar change in capitalization or event, or any dividend or distribution on our Common Stock other than an ordinary cash dividend, the Compensation Committee shall make equitable adjustments to Awards as it, in its sole discretion, deems appropriate. In the case of (1) a merger or consolidation of the Company with or into another entity pursuant to which all of our Common Stock is cancelled or converted into or exchanged for the right to receive cash, securities or other property, (2) any transfer or disposition of all of our Common Stock for

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cash, securities or other property pursuant to a share exchange or other transaction, (3) the sale or other disposition of all or substantially all of the Company’s assets, or (4) any liquidation or dissolution of the Company, the Compensation Committee may take any of a number of actions including providing for the assumption of Awards, the termination of Awards (with advance notice permitting exercise), Awards to become exercisable at or prior to the event, the liquidation of Awards or any combination of the foregoing.

The 2014 Plan also provides that any unvested Awards will generally vest immediately should a Participant be terminated by us or our successor (or should the Participant terminate for “good reason”) in connection with a “vesting change in control” within 14 days prior or 12 months after the vesting change in control.

A vesting change of control is generally defined to include, among other things: (1) a sale of us or substantially all of our assets; (2) the acquisition by a person or group of securities representing 50% or more of the voting power of the Company’s securities entitled to vote in the election of directors; or (3) certain changes in the composition of our board of directors over a period of time that are not approved by our board of directors. “Good reason” for this purpose is generally defined to include: (i) a diminution in the total annual compensation or material diminution in benefits the Participant is eligible to receive; or (ii) a requirement by us that the Participant be based at an office that is greater than 50 miles from the location of the Participant’s office immediately prior to the vesting change in control.

AMENDMENTS TO THE 2014 PLAN

Our Board may amend, suspend or terminate the 2014 Plan in whole or in part at any time provided that stockholder approval shall be required to the extent necessary under the rules applicable to ISOs or under NYSE or other applicable securities exchange rules.

The Compensation Committee may, without stockholder approval, amend the 2014 Plan as necessary to enable Awards to qualify for favorable foreign tax, securities or other treatment in the case of a Participant who is subject to a jurisdiction outside the United States.

TAX TREATMENT

The following description of the federal income tax consequences of Awards is general, does not purport to be complete, and does not describe state, local or foreign tax consequences.

TAX TREATMENT OF NONQUALIFIED STOCK OPTIONS

A Participant realizes no taxable income when an NSO is granted. Instead, the difference between the Fair Market Value of the Common Stock acquired pursuant to the exercise of the option and the exercise price paid is taxed as ordinary compensation income when the option is exercised. The difference is measured and taxed as of the date of exercise, if the Common Stock is not subject to a “substantial risk of forfeiture,” or as of the date or dates on which the risk terminates in other cases. A Participant may elect to be taxed on the difference between the exercise price and the Fair Market Value of the Common Stock on the date of exercise, even though some or all of the Common Stock acquired is subject to a substantial risk of forfeiture. Once ordinary compensation income is recognized, gain on the subsequent sale of the Common Stock is taxed as short-term or long-term capital gain, depending on the holding period after exercise. We receive no tax deduction on the grant of a nonqualified stock option, but we are entitled to a tax deduction when a Participant recognizes ordinary compensation income on or after exercise of the option, in the same amount as the income recognized by the Participant.

TAX TREATMENT OF INCENTIVE STOCK OPTIONS

Generally, a Participant incurs no federal income tax liability on either the grant or the exercise of an ISO, although a Participant will generally have taxable income for alternative minimum tax purposes at the time of exercise equal to the excess of the Fair Market Value of the Common Stock subject to the option over the exercise price. Provided that the Common Stock is held for at least one year after the date of exercise of the option and at least two years after its date of grant, any gain realized on a subsequent sale of the Common Stock will be taxed as long-term capital gain. If the Common Stock is disposed of within a shorter period of time, the Participant will recognize ordinary compensation income in an amount equal to the difference between the Fair Market Value of the stock on the date of exercise (or the sale price of the shares sold, if less) over the exercise price. We receive no tax deduction on the grant or exercise of an ISO, but we are entitled to a tax deduction if the Participant recognizes ordinary compensation income on account of a premature disposition of shares acquired on exercise of an ISO, in the same amount and at the same time as the Participant recognizes income.

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TAX TREATMENT OF STOCK APPRECIATION RIGHTS

A Participant realizes no income upon the grant of an SAR, but upon its exercise recognizes ordinary compensation income in an amount equal to the cash or cash equivalent received at that time. If the Participant receives Common Stock upon exercise of an SAR, he or she recognizes ordinary compensation income equal to the Fair Market Value of the Common Stock received (reduced, if applicable, by the base amount set forth in the related agreement), assuming the Common Stock is not subject to a substantial risk of forfeiture at exercise. We are entitled to a tax deduction in the amount of ordinary compensation income recognized.

TREATMENT OF STOCK GRANTS

A person who receives an Award of Common Stock without any restrictions will recognize ordinary compensation income equal to the Fair Market Value of the Common Stock over the amount (if any) paid. If the Common Stock is subject to restrictions, the recipient generally will not recognize ordinary compensation income at the time the Award is received but will recognize ordinary compensation income when restrictions constituting a substantial risk of forfeiture lapse. The amount of that income will be equal to the excess of the aggregate Fair Market Value, as of the date the restrictions lapse, over the amount (if any) paid for the Common Stock. Alternatively, a Participant may elect to be taxed, pursuant to Section 83(b) of the Code, on the excess of the Fair Market Value of the Common Stock at the time of grant over the amount (if any) paid for the Common Stock, notwithstanding any restrictions. All such taxable amounts are deductible by us at the time and in the amount of the ordinary compensation income recognized by the Participant.

A Participant who receives RSUs or PUs generally will not recognize ordinary compensation income at the time of grant. Rather, the Participant will generally recognize ordinary compensation income equal to the Fair Market Value of the Common Stock or cash received less the price paid, if any, at the time the RSU or PU settles shortly after vesting. When any Common Stock received is subsequently sold, the Participant generally will recognize capital gain or loss equal to the difference between the amount realized upon the sale of the shares and his or her tax basis in the shares (generally, the Fair Market Value of the stock when acquired plus any amount paid). The capital gain or loss will be long-term if the stock was held for more than one year or short-term if held for a shorter period. The Company will be entitled to a tax deduction when the Participant recognizes ordinary compensation income.

DIVIDENDS

The full amount of dividends or other distributions of property made with respect to stock grants before the lapse of any applicable restrictions will constitute ordinary compensation income, and the Company is entitled to a deduction at the same time and in the same amount as the income is realized by the Participant (unless an election under Section 83(b) of the Internal Revenue Code has been made). Dividend equivalents on RSUs and PUs will be taxed as additional ordinary compensation income at settlement, and we will be entitled to a deduction at the same time and in the same amount.

SECTION 162(M) OF THE CODE

Section 162(m) of the Code generally disallows an income tax deduction to public companies for compensation in excess of $1,000,000 paid in any year to the principal executive officer, the principal financial officer and the three other most highly compensated executive officers. In addition, each person covered by Section 162(m) of the Code for a particular year after 2016 remains subject to the $1,000,000-limit in subsequent years, even if not included in that group for the year. As noted above, TCJA eliminated after 2017 the performance-based compensation exemption. As a result, it is expected that certain of our compensation arrangements will result in non-deductible compensation when the total exceeds $1,000,000, except certain historical awards that meet transition rules for continued deductibility under the TCJA. Nevertheless, the deductibility of compensation is but one of the critical factors in the design and implementation of any compensation arrangement, and the Compensation Committee and our Board reserve the right to pay nondeductible compensation when appropriate.

AWARD INFORMATION

The benefits or amounts that may be received or allocated to any individual under the 2014 Plan are not determinable, other than amounts that may be received by each non-employee director under Iron Mountain’s existing Compensation Plan for Non-Employee Directors, which provides for an annual stock grant of that number of whole shares of Iron Mountain Common Stock determined by dividing $160,000 by the stock’s Fair Market Value on the date of grant, in addition to various cash retainers.

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PROPOSAL 3 APPROVAL OF AN AMENDMENT TO THE 2013 ESPP The Board recommends that you vote FOR the approval of an amendment to the 2013 ESPP, to increase the number of shares of Common Stock authorized for issuance thereunder by 1,000,000.

The Board has unanimously approved, and unanimously recommends that the stockholders of the Company approve, an amendment, attached hereto as Appendix B (the “ESPP Amendment”), to increase the number of shares of Common Stock authorized for issuance under the 2013 ESPP by 1,000,000 from 1,000,000 to 2,000,000. The purpose of the 2013 ESPP is to provide employees of the Company and its participating subsidiaries the opportunity to acquire an equity interest in the Company by providing favorable terms for them to purchase the Company’s Common Stock. The 2013 ESPP also includes provisions that permit the adoption of one or more subplans that may not satisfy the requirements of Section 423 of the Internal Revenue Code of 1986, as amended (the “Code”), but are designed to facilitate use of the 2013 ESPP outside the U.S. (a “2013 ESPP Subplan”).

The Board believes that equity-based compensation is a significant factor in the Company’s ability to attract, retain and motivate its employees, who are critical to the Company’s long-term success, and that an increase in the number of shares available for issuance under the 2013 ESPP will further the goal of providing employees with incentives to serve the Company.

As of March 1, 2021, only 216,287 total shares of Common Stock remained authorized for issuance under the 2013 ESPP. Unless the ESPP Amendment is approved, we do not believe that there will be enough authorized shares of Common Stock under the 2013 ESPP for regular, anticipated issuances for offering periods beginning after 2021 (based on past experience with the 2013 ESPP). The Board currently believes that the proposed increase of 1,000,000 shares of Common Stock authorized for issuance under the 2013 ESPP should result in an adequate number of shares of Common Stock for future issuance for approximately 7 years, although this forecast includes several assumptions and there are a number of factors that could impact the Company’s future Common Stock issuances. We are asking stockholders to approve the ESPP Amendment. Apart from the ESPP Amendment, no other terms or conditions of the 2013 ESPP will change.

On March 1, 2021, the closing price per share of the Company’s Common Stock, as listed on the NYSE, was $34.73.

2013 ESPP

SUMMARY OF THE 2013 ESPP

The following summary of the material features of the 2013 ESPP is qualified in its entirety by reference to the complete text of the 2013 ESPP, attached as Appendix A to the Company’s Proxy Statement on Schedule 14A filed on April 24, 2013. The summary of the 2013 ESPP set forth below assumes the approval of the ESPP Amendment and is qualified in its entirety by reference to the 2013 ESPP as proposed to be amended. As noted above, other than the change to the 2013 ESPP proposed to be made by the ESPP Amendment, no other terms or conditions of the 2013 ESPP will change.

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 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 customers’ IT infrastructure, with reliable and flexible deployment options.

The 2013 ESPP operates by granting,Founded in an underground facility near Hudson, New York in 1951, we had approximately 225,000 customers in a seriesvariety of offerings, options to acquireindustries in 63 countries around the Company’s Common Stock. The Compensation Committee, which has been delegated authority to administer the 2013 ESPP by the Board, determines the commencement date and duration of offerings. The Compensation Committee may also limit the maximum amount of Common Stock available with respect to an offering.

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CORPORATE GOVERNANCE MATTERS

Offerings under the 2013 ESPP generally last for six months and begin each June 1 and December 1 (or the preceding business day). During an offering, payroll deductions are accumulated on behalf of each participant. At the end of each offering, options issued under the 2013 ESPP are exercised and the accumulated payroll deductions are retained by the Company as full payment of the option price. Each participant receives a number of whole shares of the Company’s Common Stock equal to the accumulated payroll deductions credited to the participant’s accountworld as of the exercise date divided by the option price. In generalDecember 31, 2021. We currently serve customers across an array of market verticals - commercial, legal, financial, healthcare, insurance, life sciences, energy, business services, entertainment and except in the case of cash in lieu of a fractional share, any excess cash remaining at the close of an offering is not carried over to the next offering and is instead returned to a participant, without earnings.

The “option price” of shares of Common Stock under the 2013 ESPP can be as low as 85% of the lower of the fair market value of the Company’s shares at the start of the offering or on the exercise date. However, the 2013 ESPP utilizes an option price ofgovernment organizations, including approximately 95% of the fair market valueFortune 1000. As of the Company’s shares on the exercise date. Fair market value under the 2013 ESPP generally means the average of the highest and lowest sale price of the Company’s Common Stock on the date in question.December 31, 2021, we had approximately 25,000 employees.

The Compensation Committee may adopt one or more 2013 ESPP Subplan(s) in order to facilitate participation by employees in countries that have local laws that may be inconsistent with Section 423 of the Code. In general, however, the key terms and conditions of any such 2013 ESPP Subplan will reflect the same terms and conditions of the 2013 ESPP as offered to eligible U.S. employees to the extent possible.

SHARES AVAILABLE UNDER THE 2013 ESPP

After giving effect to the ESPP Amendment, the total number of authorized shares that may be subject to options under the 2013 ESPP is 2,000,000. After giving effect to the ESPP Amendment, we project that there will be enough shares to keep the 2013 ESPP in place through 2028. The Compensation Committee may impose a cap on the amount of Common Stock available with respect to any offering, and has historically done so under the 2013 ESPP.

If an option expires or is terminated or surrendered, the shares allocable to the option may again be available under the 2013 ESPP. If insufficient shares are available at the end of an offering, a pro rata allocation of remaining shares will be made.

We intend to register the new shares reserved for issuance under the 2013 ESPP on a Registration Statement on Form S-8 under the Securities Act of 1933, as amended, as soon as practicable after receiving stockholder approval.

ELIGIBILITY AND PARTICIPATION

In general, any employee of the Company or a participating subsidiary that is (or is treated for federal income tax purposes as) a corporation who is customarily employed for more than five months in a calendar year and has performed services for the Company or a participating subsidiary for at least six months may become a participant in any future offering under the 2013 ESPP by electing to participate prior to the commencement of the offering. However, the following persons are ineligible to participate in the 2013 ESPP: (1) any employee who owns, directly or indirectly, as of the start of an offering, 5% or more of the Company’s stock or the stock of one of the Company’s corporate subsidiaries; (2) any employee of a subsidiary that is either ineligible to or does not elect to participate in the 2013 ESPP; (3) any union employee, if the union elects not to participate in the 2013 ESPP; and (4) any individual who is not an employee, including outside directors, consultants, and independent contractors. In addition, an employee will not be granted an option that would permit him or her to own (or be considered to own) or hold outstanding options to purchase 5% or more of the total combined voting power or value of all classes of the Company’s stock or that of a corporate subsidiary, and a participant cannot acquire in any year more than $25,000 worth of the Company’s stock under the 2013 ESPP (based on the value of the Company’s stock at the start of the offering). At this time, approximately 9,000 persons are considered by the Company to be eligible to receive options pursuant to the 2013 ESPP.

A participant may authorize payroll deductions of 1-15% of the participant’s cash compensation on each pay date. A participant can decrease his or her rate of payroll deductions, but the participant can never increase the rate of payroll deductions once an offering begins.

A participant may, prior to the end of an offering period, and at such time and in such manner as the Compensation Committee may prescribe, withdraw from an offering and request payment of an amount in cash equal to the accumulated payroll deductions credited to the participant’s account under the 2013 ESPP. In no event will a participant receive interest with respect to his or her payroll deductions, whether used to exercise options or returned in cash.

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CORPORATE GOVERNANCE MATTERS

TERMINATION OF EMPLOYMENT

Upon termination of employment for any reason other than death, the participant will receive a payment in cash of the amount credited to the participant’s account under the 2013 ESPP. In the event that a participant dies prior to the end of an offering period, the participant’s account will be paid in cash to his or her estate.

RESTRICTIONS ON TRANSFER

A participant may not transfer, assign, pledge or otherwise dispose of an option issued under the 2013 ESPP. Shares acquired under the 2013 ESPP at the end of an offering period will be freely tradable, subject in all cases to the participant’s compliance with the Company’s Statement of Insider Trading Policy.

ADMINISTRATION

The 2013 ESPP was approved by the Board on March 14, 2013 and approved by stockholders on June 6, 2013. The 2013 ESPP is administered by the Compensation Committee. The Compensation Committee has the authority to adopt, amend, and rescind such rules and regulations as, in its opinion, may be advisable in the administration of the 2013 ESPP and to decide all questions of interpretation and application of such rules and regulations, which decision will be final and binding.

FORFEITURE FOR DISHONESTY

If the Board determines that a participant has engaged in fraud, embezzlement, theft, commission of a felony or proven dishonesty in the course of his or her employment that has damaged the Company or a subsidiary or has disclosed trade secrets or other proprietary information of the Company or a subsidiary, (1) the individual’s participation in the 2013 ESPP will terminate and the participant will forfeit his or her right to receive any Common Stock that has not been delivered pursuant to an offering and (2) the Company will have the right to repurchase all or any part of the shares of Common Stock acquired by the participant upon the earlier exercise of any option pursuant to the 2013 ESPP, at a price equal to the amount paid to the Company upon exercise, together with interest.

EFFECT OF CERTAIN CORPORATE CHANGES

If, before an offering closes, the Company merges or consolidates with one or more corporations (whether or not the Company is the surviving corporation), or the Company is liquidated, sells or otherwise disposes of substantially all of its assets to another entity, or there is a “change of control,” as defined in the 2013 ESPP, then the Compensation Committee, in its discretion, may either: (1) convert outstanding options such that after the effective date of the event, each participant is entitled upon exercise to receive, in lieu of the Company’s Common Stock, the number and class of shares of the stock or other securities to which the participant would have been entitled had the participant been a stockholder at the time of the event; or (2) end the offering and exercise the options as of the day before the effective date of the event.

A “change of control,” for the purposes of the 2013 ESPP, shall be deemed to have occurred if any person (as such term is used in Section 13(d) and 14(d)(2) of the Exchange Act) other than a trust related to an employee benefit plan maintained by the Company becomes the beneficial owner (within the meaning of Rule 13d-3 under the Exchange Act) of 50% or more of the Company’s outstanding Common Stock, and, within the period of 24 consecutive months immediately thereafter, individuals other than (1) individuals who at the beginning of such period constitute the entire Board or (2) individuals whose election, or nomination for election by the Company’s stockholders, was approved by a vote of at least two-thirds of the directors then still in office who were directors at the beginning of the period, become a majority of the Board.

2013 ESPP SUBPLAN(S)

The Compensation Committee may adopt one or more 2013 ESPP Subplan(s) and such rules and regulations as, in its opinion, may be advisable in the administration of a 2013 ESPP Subplan in order to accommodate the specific requirements of local laws and procedures outside the U.S. The terms and conditions of any such 2013 ESPP Subplan may differ as necessary to accommodate local law (including, without limitation, as necessary to obtain preferential local tax treatment), but in no event will the authority of the Board, as set forth in the next paragraph, be altered by any such arrangement.

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AMENDMENT OR TERMINATION

The Board may at any time, without a vote by stockholders, terminate or, from time to time, amend, modify or suspend the 2013 ESPP; provided, however, that without stockholder approval there will be no: (1) change in the number of shares of Common Stock that may be issued under the 2013 ESPP; (2) change in the class of persons eligible to participate in the 2013 ESPP; or (3) other change to the 2013 ESPP that requires stockholder approval under applicable law. Unless terminated earlier, the 2013 ESPP will terminate on the date as of which there are no longer any shares of Common Stock available to be offered.

The following description of the federal income tax consequences of the 2013 ESPP is general and does not purport to be complete. In addition, the description does not discuss the tax consequences arising as a result of the participant’s death or of the tax consequences of the 2013 ESPP under the laws of any state or foreign country in which the participant may reside.

FEDERAL INCOME TAX CONSEQUENCES OF THE 2013 ESPP

Except as may be the case in the event of any 2013 ESPP Subplan(s), the 2013 ESPP is intended to constitute an “employee stock purchase plan” under Section 423 of the Code. As presently in effect, under Section 423 of the Code, a participant will not realize income as a result of either the grant of an option at the start of an offering period or the exercise of an option at the end of an offering period and the Company will not be entitled to an income tax deduction at such grant date or exercise date. If the participant holds the stock acquired under the 2013 ESPP until the earlier of two years after the start of an offering or one year after the end of an offering, then upon the subsequent sale of the stock, the participant will have ordinary compensation income of the lesser of 5% of the fair market value of the stock as of the start of the offering or the excess, if any, of the selling price of the stock over the option price. Any additional gain or loss will be treated as long-term capital gain or loss. The Company is not entitled to an income tax deduction with respect to the ordinary compensation income described above.

If the participant disposes of any Common Stock acquired under the 2013 ESPP before the earlier of two years after the start of the offering or one year after the end of the offering, then the excess, if any, of the fair market value of the Common Stock at the end of the offering over the option price will be ordinary compensation income to the participant, and the Company will be entitled to a deduction with respect to that income. Any additional gain or loss will be treated as short-term or long-term capital gain or loss, depending on the holding period.

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EXECUTIVE COMPENSATION

PROPOSAL 4 APPROVAL, BY A NON-BINDING ADVISORY VOTE, OF THE COMPENSATION OF OUR NAMED EXECUTIVE OFFICERS The Board recommends that you vote FOR the approval of the non-binding, advisory resolution approving the compensation of our Named Executive Officers.

In accordance with the requirements of Section 14A of the Exchange Act and related rules of the SEC, we are including this separate proposal for stockholders to approve, on a non-binding, advisory basis, the compensation of our named executive officers listed in the Summary Compensation Table appearing on page 69 of this Proxy Statement (collectively, our “Named Executive Officers” or our “NEOs”).

Our executive compensation is designed to reward performance that contributes to long-term success of the Company and our stockholders and to attract, motivate, 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 for performance” philosophy that links competitive levels of executive compensation to achievements of our overall strategy and business goals, including 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 Discussion and Analysis” section of this Proxy Statement and the compensation tables and the other narrative compensation disclosures contained in this Proxy Statement for additional details on our executive compensation, including our compensation philosophy and objectives and the compensation of our 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 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 NEOs as disclosed in this Proxy Statement, the Compensation Committee will evaluate whether any actions are necessary to address the concerns of stockholders.

As a result of adverse macroeconomic uncertainties created by the COVID-19 pandemic and other related conditions outside of our control that affected our financial performance in fiscal 2020, the Compensation Committee elected to adjust the challenging performance goals set for our fiscal 2020 short-term incentive cash bonus plan but limit the corporate performance payout for the executives at 85% of target bonus opportunity.

We believe the compensation paid to our NEOs for fiscal 2020 appropriately reflects and rewards our executive officers’ contributions to the performance of Iron Mountain despite the adverse macroeconomic impact of the COVID-19 pandemic 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, that the compensation paid to the Company’s Named Executive Officers, as disclosed pursuant to Item 402 of Regulation S-K, including theThis Compensation Discussion and Analysis compensation tablesexplains the guiding principles and narrative discussion in the Proxy Statement for the 2021 Annual Meetingpractices of Stockholders, is hereby APPROVED.”

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EXECUTIVE COMPENSATION

COMPENSATION DISCUSSION AND ANALYSIS

EXECUTIVE OVERVIEW

Our executive compensation program reflects our pay for performance compensation philosophy and goals. This section describes our executive compensation program and the compensation ofpaid to the individuals who served as our chiefa named executive officer in 2021. The 2021 compensation of our named executive officers appropriately reflects and chief financial officer in 2020, and our other NEOs, including specific factors considered in our compensation decision-making process.

NAMED EXECUTIVE OFFICERS

rewards their significant contributions across Iron Mountain’s NEOs provide exceptional leadership across our global businesses.

Together with the other members of our executive team, these leaders advance the strategic and operational results that drive stockholder value. Our NEOs as of December 31, 20202021 were:

COMPENSATION PHILOSOPHY AND PRACTICES

2020 PERFORMANCE AND PAY HIGHLIGHTS

WeOur executive compensation programs are a leading providerdesigned to attract, retain and focus the talents and energies of physicalour executives on meeting the current and digital information storage and retrieval, with approximately 24,000 employees serving a broad range of industries and government organizations. With a global real estate footprint of approximately 1,450 owned and leased facilities totaling approximately 93 million square feet of space, we provide (i) storage and information management services and digital solutions in 56 countries on six continents (storing approximately 710 million cubic feet of hard-copy records) and (ii) enterprise-class data center facilities and hyperscale-ready capacity in the United States, Europe and Asia (with 130 megawatts of leasable capacity operating and total potential capacity of approximately 376 megawatts) as of December 31, 2020.

(1) IRON MOUNTAIN’S RESPONSE TO THE COVID-19 PANDEMIC

Although fiscal 2020 was a challenging year, following the onsetfuture objectives of the COVID-19 pandemic in March 2020, management took immediate actionsCompany and are guided by the following design principles:

General Program Competitiveness – In order to minimizeattract and retain top performing executives, we establish overall Total Direct Compensation (“TDC”) with reference to relevant external benchmarks. We define TDC as base salary plus short-term incentive compensation plus long-term incentive compensation. In addition, the spreadpositioning of each executive’s pay relative to market benchmarks reflects experience, proficiency, strategic importance, and performance of required duties.

Pay for Performance – The majority of compensation for our NEOs is performance-based. We award short- and long-term variable, performance-based compensation intended to deliver target compensation when established goals are met with the viruspotential for above-target compensation (up to a maximum) when rigorous goals are met and limit its impact on our people, customers, businessbelow-target compensation when established goals are not met.

Internal Parity – The overall target TDC opportunity for each executive reflects the responsibility, scope and operations. Protectingcomplexity of that individual’s role within the healthCompany.

Alignment with Business Strategies and safetyShareholders – Our executive compensation programs reward achievement of enterprise financial goals and strategic objectives that drive long-term shareholder value creation, thereby aligning the interests of our global employees and meeting the ongoing needs ofexecutives with our customers and communities around the world was paramount. Focusing on those things that were under its control, management expertly and swiftly executed through difficult and unprecedented circumstances and took significant action in response to the disruption caused by the COVID-19 pandemic, including:

shareholders.

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EXECUTIVE COMPENSATION

We maintain the following policies and practices that drive our executive compensation programs:

2021 PERFORMANCE AND PAY HIGHLIGHTS

(2) 2020Throughout 2021, our core business has remained resilient, supported by our broad offerings, deep customer relationships, and the team’s steady execution of our strategic plan. In 2021, Iron Mountain achieved record levels of quarterly revenue, experienced increased demand for our services across key markets, saw strong uptake in our digital and secure offerings, and drove continued momentum in our data center business.

2021 FINANCIAL AND OPERATIONAL PERFORMANCE

Prior toDespite the onsetcontinued impacts of the COVID-19 pandemic, we wereincluding the Omicron variant, on course to exceed our financialbusiness, our core business has remained resilient, supported by our broad offerings, deep customer relationships, and operational goalsthe management’s steady execution of our strategic plan. In 2021, Iron Mountain achieved record levels of quarterly revenue, experienced increased demand for fiscal 2020, which was evidentour services across key markets, saw strong uptake in our strong performance throughdigital and Secure IT Asset Disposition offerings, and drove continued momentum in our data center business.

For the first quarteryear ended December 31, 2021, our revenue was $4.5 billion, which increased 8% on a reported basis year on year and over 6% on an organic constant currency basis year on year. Adjusted EBITDA⁽²⁾ increased 11% on a reported basis year on year to $1.635 billion, and we achieved the high end of 2020. Following the onset of the COVID-19 pandemic, however, we concluded that, given the extreme level of economic uncertainty, it would be prudentfull year guidance despite foreign currency exchange headwinds. Adjusted Funds from Operations (“AFFO”)⁽³⁾ increased 14% to withdraw$1.0 billion or $3.48 on a per-share basis year on year. Both Adjusted EBITDA and AFFO exceeded our previously issued 2020 financialfull year 2021 guidance. In the final nine months ofAdditional fiscal 2020, we continued to execute our strategy while meeting or exceeding our revised internal financial performance expectations. Despite significant COVID-19 pandemic-related headwinds, our fiscal 20202021 financial and operational performance highlights include: