You are cordially invited to attend the 20182019 Annual Meeting of Stockholders of Great Western Bancorp, Inc., to be held at The Phoenician, 6000 E. Camelbackthe Hyatt Regency Scottsdale Resort & Spa at Gainey Ranch, 7500 East Doubletree Ranch Road, Scottsdale, Arizona on Thursday, February 22, 2018,21, 2019, at 9:00 a.m. Mountain Standard Time, or any adjournment thereof (the "Annual Meeting"), for the following purposes:

The Record Date for determining stockholders entitled to notice of, and to vote at, the Annual Meeting was the close of business on January 5,December 28, 2018. A list of stockholders entitled to vote at the Annual Meeting will be available for inspection upon request of any stockholder for a purpose germane to the Annual Meeting at our principal executive offices at 225 S. Main Ave., Sioux Falls, South Dakota 57104 during the ten days prior to the Annual Meeting, during ordinary business hours, and at The Phoenician, 6000 E. Camelbackthe Hyatt Regency Scottsdale Resort & Spa at Gainey Ranch, 7500 East Doubletree Ranch Road, Scottsdale, Arizona, during the Annual Meeting.

These proxy materials are furnished in connection with the solicitation by the Board of Directors (the “Board” with individual members of the Board being referred to herein as a “director”) of Great Western Bancorp, Inc., a Delaware corporation ("theGreat Western", "GWB", "we", "our", "us" and "the Company"), of proxies to be voted at the 20182019 Annual Meeting of Stockholders of the Company and at any adjournment of such meeting (the “Annual Meeting”). In accordance with rules and regulations of the Securities and Exchange Commission (the "SEC"), instead of mailing a printed copy of our proxy materials to each stockholder of record, we furnish proxy materials, which include this Proxy Statement (this “Proxy Statement”), and the accompanying proxy card, Notice of Annual Meeting, and Annual Report on Form 10-K for fiscal year ended September 30, 2017,2018, to our stockholders by making such materials available on the Internet unless otherwise instructed by the stockholder. If you received a Notice of Internet Availability of Proxy Materials (the "Notice") by mail and would like to receive a printed copy of our proxy materials by mail or an electronic copy of our proxy materialmaterials by email, you should follow the instructions for requesting such materials included in the Notice, which is first being mailed to stockholders on or about January 10, 2018.11, 2019. The Notice will also contain instructions for accessing our proxy materials on the Internet.

In connection with our initial public offering in October 2014 (the “Offering”), Great Western Bancorp, Inc. merged with Great Western Bancorporation, Inc., an Iowa corporation (“GWBI”), with Great Western Bancorp, Inc. continuing as the surviving corporation and succeeding to the business of GWBI. When used in this Proxy Statement, the terms “Great Western,” “GWB,” “we,” “our,” “us” and the “Company” refer, prior to the completion of the merger, to GWBI and, following the completion of the merger, to Great Western Bancorp, Inc. In addition, the term “our Bank” refers to Great Western Bank, a South Dakota banking corporation and our wholly owned subsidiary, as a result of our merger with GWBI, and the term “fiscal year” refers to our fiscal year, which is based on a twelve-month period ending September 30 of each year (e.g., fiscal year 20172018 refers to the twelve-month period ending September 30, 2017)2018).

The Annual Meeting will be held on Thursday, February 22, 201821, 2019 at 9:00 a.m. Mountain Standard Time, at The Phoenician, 6000 E. Camelbackthe Hyatt Regency Scottsdale Resort & Spa at Gainey Ranch, 7500 East Doubletree Ranch Road, Scottsdale, Arizona.

At the Annual Meeting, stockholders will act upon the matters described in the Notice of Annual Meeting that accompanies this Proxy Statement, including (i) the election of threetwo nominees for director named in this Proxy Statement; (ii) the approval, on an advisory (non-binding) basis, of the Company's executive compensation as described in this Proxy Statement; (iii) approval of an amendment to the Company's 2014 Omnibus Incentive Compensation Plan increasing the number of authorized shares from 813,889 to 1,375,889, (iv) approval of an amendment to the Company's 2014 Non-Employee Director Plan increasing the number of shares from 83,333 to 121,333, and (v)(iii) the ratification of the Audit Committee’s appointment of Ernst & Young LLP as Great Western’s independent registered public accounting firm for fiscal year 2018.2019.

Only record holders of our common stock, par value $0.01 per share (“Common Stock”), as of the close of business on January 5,December 28, 2018 (the “Record Date”), will be entitled to vote at the Annual meeting.Meeting. On the Record Date, the Company had outstanding 58,896,18956,938,435 shares of Common Stock. Each outstanding share of Common Stock entitles the holder to one vote.

The Annual Meeting will be held only if a quorum is present. A quorum will be present if a majority of the shares of Common Stock outstanding on the Record Date are represented, in person or by proxy, at the Annual Meeting. Shares represented by properly completed proxy cards either marked “abstain” or “withhold,” or returned without voting instructions, are counted as present for the purpose of determining whether a quorum is present at the Annual Meeting. Also, if shares are represented by properly completed proxy cards, but are held by brokers who are prohibited from exercising discretionary authority for beneficial owners who have not given voting instructions (“broker non-votes”), those shares will be counted as present for the purpose of determining whether a quorum is present at the Annual Meeting.

The deadline for voting by telephone or on the Internet is 1:00 a.m. Central Time on February 22, 2018.

If you hold your shares through a broker, bank or other nominee, that institution will instruct you as to how your shares may be voted by proxy, including whether telephone or Internet voting options are available. If you hold your shares through a broker, bank or other nominee and would like to vote in person at the Annual Meeting, you must first obtain a copy of the voting instruction card provided by your broker, bank or nominee or a copy of a brokerage statement showing your ownership of shares as of January 5,December 28, 2018.

If you vote other than by phone or Internet, you may change your vote at any time before the actual vote takes place at the Annual Meeting. If you vote by phone or Internet, you may change your vote if you do so prior to 1:00 a.m. Central Time on February 22, 2018.21, 2019. If you hold your shares through a broker, bank or other nominee, that institution will instruct you as to how your vote may be changed.

The Company’s tabulator,inspector, Computershare, will count the votes.

Yes. As a matter of policy, stockholder proxies, ballots and tabulations that identify individual stockholders are kept secret and are available only to the Company, its inspector and proxy solicitor, who are required to acknowledge their obligation to keep your votes confidential.

With respect to any other business that may properly come before the Annual Meeting, or any adjournment of the Annual Meeting, that is submitted to a vote of the stockholders, including whether or not to adjourn the Annual Meeting, your shares will be voted in accordance with the best judgment of the persons voting the proxies.

We will treat broker non-votes as present to determine whether or not we have a quorum at the Annual Meeting, but they will not be treated as entitled to vote on the proposals, if any, for which the broker indicates it does not have discretionary authority.

If any matters other than those referred to in the Notice of Annual Meeting properly come before the Annual Meeting, the individuals named in the accompanying proxy card will vote the proxies held by them in accordance with their best judgment. The Company is not aware of any business other than the items referred to in the Notice of Annual Meeting that will be considered at the Annual Meeting.

Because many stockholders cannot personally attend the Annual Meeting, it is necessary that a large number be represented by proxy in order to satisfy the requirement that a quorum be present to conduct business at the Annual Meeting. Whether or not you plan to attend the meeting in person, prompt voting by proxy will be appreciated. Stockholders of record can vote their shares via the Internet or by using a toll-free telephone number. Instructions for using these convenient services are provided in the Notice or on the proxy card. Of course, you may still vote your shares on the proxy card. To do so, we ask that you complete, sign, date and return the enclosed proxy card promptly in the postage-paid envelope.

The Board does not have a policy regarding the separation of the roles of Chief Executive Officer and Chairman of the Board, as the Board believes it is in the best interests of the Company for the Board to have the flexibility to make that determination from time to time based on the position and direction of the Company and the membership of the Board. Currently, the Board believes the positions of Chairman and Chief Executive Officer should be held by the same person, as this combination is serving the Company well by providing unified leadership and direction.

Mr. Karels currently serves as Chairman President and Chief Executive Officer of the Company. The Board has determined that this structure presently makes the best use of Mr. Karels' extensive knowledge of the Company and the financial services industry, as well as his ability to foster communication between the Company's management and the Board.

It is the policy of the Board to appoint a lead independent director when the role of Chairman and Chief Executive Officer are combined. The Board recognizes that a lead independent director selected by the other independent directors can facilitate the process and controls that support a strong and independent board and strengthen the cohesiveness and effectiveness of the Board as a whole. The lead independent director has the general responsibility to preside at all meetings of the Board when the Chairman is not present and during executive sessions of the independent directors. The lead independent director also, among other things, serves as the liaison between the independent directors and the Chairman, and collaborates with the Chairman to set meeting schedules and agendas. Our Board believes that this structure combines experience and accountability with effective oversight.

The lead independent director of the Board is chosen by the independent directors of the Board. Thomas E. Henning, who is an independent director under the listing standards adopted by the New York Stock Exchange ("NYSE") and Rule 10A-3 of the Securities Exchange Act of 1934 (the "Exchange Act"), is currently our lead independent director. Mr. Henning has served in this role since February 2017.

In addition, the members of our Board are also members of the Bank's Board of Directors, and as such are actively involved in the Bank's risk oversight activities and the policy approval function of the Board of Directors of the Bank.

Our senior management and Management Risk Committee ("MRC") are responsible for implementing and reporting to our Board regarding our risk management processes, including by assessing and managing the risks we face, including strategic, operational, legal, compliance, technology, regulatory, investment and execution risks, on a day-to-day basis. Our MRC derives its authority from our Risk Committee and its members include our President and CEOChief Executive Officer (Chairperson), President, Chief Financial Officer, Chief Risk Officer, Regional President, Chief Credit Officer, General Counsel, General Manager Strategic Business Services, Treasurer, Senior Vice President Operations, Chief Information Officer and Head of Enterprise Risk Management, Head of Risk Asset Review, Operational RiskPeople & Compliance Manager, Bank Secrecy Act ManagerCulture and Chief Information Officer.Learning & Development. Our senior management and MRC are also responsible for creating and recommending to our Board and Risk Committee for approval appropriate risk appetite metrics reflecting the aggregate levels and types of risk we are willing to accept in connection with the operation of our business and pursuit of our business objectives.

The role of our Board in our risk oversight is consistent with our leadership structure, with our President and Chief Executive Officer and the other members of senior management having responsibility for assessing and managing our risk exposure, and our Board and its committees providing oversight in connection with those efforts. We believe this division of risk management responsibilities presents a consistent, systemic and effective approach for identifying, managing and mitigating risks throughout our operations.

The Audit Committee must consist of at least three members, each of whom must meet financial competency standards and be “independent” under the listing standards of the NYSE and meet the requirements of Rule 10A-3 of the Exchange Act. The members of the Audit Committee include Ms. Grieb (Chairperson) and Messrs. Brannen and Israel, each of whom satisfy the foregoing requirements. The Board has determined that Ms. Grieb, Mr. Brannen and Mr. Israel each qualify as an audit committee financial expert.

The Compensation Committee must consist of at least three members, each of whom must meet NYSE’s independence standards. The members of the Compensation Committee are Messrs. Rykhus (Chairperson), Lacy and Spies, each of whom satisfies the independence standards.

The Governance Committee must consist of at least three members, each of whom must meet NYSE’s independence standards. The members of the Governance Committee are Messrs. Lacy (Chairperson), Rykhus and Spies, each of whom satisfies the independence standards.

The Risk Committee must consist of at least three members, a majority of whom must be independent, including the Chairperson. The members of the Risk Committee are Messrs. Brannen (Chairperson), Henning and Israel and Ms. Grieb, each of whom satisfies the independence standards. The Board has determined that Messrs. Brannen, Henning, and Israel have the requisite experience in identifying, assessing and managing the risk exposures of large, complex firms and each qualify as a risk committee risk management expert.exposures.

The Company’s Secretary and General Counsel will distribute to the director addressee(s) all communications that, in his or her judgment, are appropriate for consideration by the director(s). Examples of communications that would be considered inappropriate for consideration by the directors include, but are not limited to, commercial solicitations, trivial, obscene or profane items, administrative matters, ordinary business matters, job inquiries, or personal grievances. Correspondence that is not appropriate for Board review will be handled by our Company’s Secretary and General Counsel. All appropriate matters pertaining to accounting or internal controls will be distributed promptly to the attention of the Chairperson of the Audit Committee.

In the event the Chairperson is not an independent director, the Board will appoint a Lead Independent Director who will receive an additional annual cash retainer of $20,000.Director. During fiscal year 2017,2018, the Company appointed Mr. Henning to serve as Lead Independent Director.

We also reimburse all directors for reasonable out-of-pocket expenses incurred in connection with the performance of their duties as directors, including without limitation travel expenses in connection with their attendance in-person at Board and committee meetings.

Certain decisions and transactions are not subject to the related party transaction approval policy, including: (i) decisions on compensation or benefits relating to directors or executive officers and (ii) loans or other indebtedness owing to us made in the ordinary course of business, on substantially the same terms, including interest rate and collateral, as those prevailing at the time for comparable loans with persons not related to us and not presenting more than the normal risk of collectability or other unfavorable features.

Section 16(a) of the Exchange Act requires directors, executive officers and greater than 10% beneficial owners of the Company’s Common Stock to file reports concerning their ownership of and transactions in such Common Stock. Based on a review of these reports filed by the Company’s officers, directors and shareholders, the Company believes that its officers, directors and shareholders complied with all filing requirements under Section 16(a) of the Exchange Act during fiscal year 2017.2018.

Our Board is currently composed of eight members. Each of our directors is elected for a three-year term, classified into three staggered classes (designated as Class I, II and III). At each annual meeting of stockholders, upon the expiration of the term of a class of directors, the successor to each such director in the class will be elected to serve from the time of election and qualification until the third annual meeting following his or her election and until his or her successor is duly elected and qualified. At the Annual Meeting, you will be asked to elect threetwo individuals to serve on the Board until the 20212022 Annual Meeting of Stockholders and until a successor shall have been elected and qualified.

The Governance Committee seeks candidates for nomination to the Board who possess the background, skills and expertise to make a significant contribution to the Board, the Company and its stockholders. The Governance Committee uses a variety of methods to identify and evaluate nominees for director. The Governance Committee periodically assesses the appropriate size of the Board and whether any vacancies on the Board are expected. In the event that vacancies are anticipated or otherwise arise, the Governance Committee will seek to identify director candidates, subject to the restrictions described below, based on input provided by a number of sources, including Governance Committee members, other directors and our management and stockholders. The Governance Committee also has the authority to consult with or retain advisors or search firms to assist in the identification of qualified director candidates.

Although the Company has no formal policy regarding diversity, the Governance Committee and the Board believe that the Board should include directors with diverse experience and business knowledge and believes that the directors and director nominees bring a diverse range of perspectives to the Board’s deliberations. The Governance Committee considers director qualifications according to the particular areas of expertise being sought as a complement to the existing Board composition at the time. Qualifications include, among others, high-level leadership experience in business activities, breadth of knowledge about issues affecting the Company and our Bank, understanding of the customers served by our Bank, a willingness to promote the success and economic growth of the Company and our Bank and time available for meetings and consultation on matters of the Company and our Bank. When considering potential director candidates, our Governance Committee also considers the candidate’s character, judgment, diversity, skills, including financial literacy, and experience in the context of our needs and those of the Board. Additionally, no individual may be nominated for election or elected as a director if, on the date of election, the individual would be age 75 or older.

Under the corporate governance guidelines adopted by the Board, all directors are expected to own Common Stock having a value of at least four times the annual Board retainer fee, exclusive of any committee and chairperson fees, no later than five years after the later of January 1, 2015 or the date such person became a director and to limit board service at other public companies to no more than four other public company boards.

The Board, acting pursuant to the recommendation of the Governance Committee, has nominated each director standing for re-election. Each of the nominees currently serves as a director. In considering the nominees’ individual experience, qualifications, level of Board and committee participation, quality of performance, attributes and skills, the Governance Committee and the Board have concluded that when considered together with the directors continuing in office, the appropriate experience, qualifications, attributes and skills are represented for the Board as a whole and for each of the Board’s committees. There are no family relationships among any directors, director nominees and executive officers. Each nominee has indicated a willingness to serve, and the Board has no reason to believe that any of the nominees will not be available for election. However, if any of the nominees are not available for election, proxies may be voted for the election of other persons selected by the Board. Proxies cannot, however, be voted for a greater number of persons than the number of nominees named. Stockholders of the Company have no cumulative voting rights with respect to the election of directors.

Long-term incentive compensation opportunities are provided to the NEOs through the award of annual grants under the LTI Plan.

The Compensation Committee believes these employment arrangements are an important part of overall compensation for our NEOs and will help to secure the continued employment and dedication of our NEOs, prior to or following a change in control, notwithstanding any concern that they might have at such time regarding their own continued employment. These agreements also contain restrictive covenants, including non-compete and non-solicitation provisions, which protect the Company's interests in its client and employee relationships. The Compensation Committee also believes that these agreements are important as a recruitment and retention device, as nearly all of the companies with which we compete for executive talent have similar agreements in place for their senior employees.

In addition, the clawback provision of the Sarbanes-Oxley Act of 2002 also applies to our NEOs. This provision provides that if the Company is required to restate its financial statements as a result of misconduct, the NEOs are required to reimburse the Company for bonuses or other incentive-based or equity-based compensation and profits realized during the three completed fiscal years immediately preceding the date on which the Company is required to prepare an accounting restatement.

Each employment agreement provides for, among other things: (i) an annual base salary of $715,000$825,000 for Mr. Karels, $345,000$400,000 for Mr. Chapman, and $285,000$535,000 for Mr. Ulenberg, and $278,000Bass, $275,000 for Mr. Bass;Gough and $255,000 for Ms. Knieriem; (ii) an annual incentive bonus under the STI Plan with a target opportunity of 75%85% of base salary for Mr. Karels, 50%60% for Messrs.Mr. Chapman, and Ulenberg and65% for Mr. Bass, 30% for Mr. BassGough and 20% for Ms. Knieriem with the actual amount earned ranging from 0% to 200% of target based on actual achievement against performance; (iii) annual long-term incentive compensation awards under the LTI Plan with a value of $670,000$915,000 for Mr. Karels, $225,000$255,000 for Mr. Chapman, $175,000$455,000 for Mr. Ulenberg, and $100,000Bass, $85,000 for Mr. Bass,Gough, and $85,000 for Ms. Knieriem, and eligibility to receive future annual long-term incentive compensation awards in form and amount determined in the sole discretion of our Board and (iv) participation in our employee benefit and welfare plans. The annual long-term incentive compensation awards for the 2015 fiscal year are 50% in the form of time-based restricted stock units that vest in three equal annual installments on each of the first three anniversaries of the grant date and 50% in the form of performance-based restricted stock units that cliff vest based on performance over a three-year performance period. Each of Messrs. Chapman and Ulenberg also received an additional $10,000 per month for 12 months as they transitioned from their international assignments, payments of which ceased December 31, 2015. The NEOs also received a special one-time grant of performance-based restricted share units immediately following the completion of our Offering with an initial value of $1,000,000 for Mr. Karels, $225,000 for Mr. Chapman, $175,000 for Mr. Ulenberg and $100,000 for Mr. Bass. The grants vested on September 30, 2017 based on performance over a three-year performance period.

Upon a termination of any of the NEO’s employment by the Company without “cause” or by such NEO for “good reason”, subject to a general release of claims in favor of the Company, the NEO will be entitled to: (i) a prorated annual incentive bonus under the STI Plan for the year of termination based on actual performance; (ii) a severance payment equal to two times for Mr. Karels, and one times for Messrs. Chapman, Ulenberg,Bass, Gough and Bass,Ms. Knieriem, the sum of (A) the NEO’s then-current annual base salary and (B) the NEO’s then-current target annual incentive bonus, paid in 52 or 26 equal installments, respectively, in accordance with the Company’s normal payroll practices; (iii) either (A) continued benefits under the Company’s group healthcare, vision and dental plans through the second anniversary of termination of employment for Mr. Karels, and through the first anniversary for Messrs. Chapman, Ulenberg,Bass, Gough and Bass,Ms. Knieriem, or (B) a lump-sum payment (grossed up for applicable taxes) equal to 24 times for Mr. Karels, and 12 times for Messrs. Chapman, Ulenberg,Bass, Gough and BassMs. Knieriem, the monthly Consolidated Omnibus Budget Reconciliation Act of 1985 ("COBRA") cost of continued health and medical coverage and (iv) continued vesting of any outstanding equity compensation awards under the LTI Plan as if the executive had remained employed through the applicable vesting dates. In the event that the NEO’s employment is terminated by the Company without “cause” or by the executive for “good reason”

“Cause” generally means the NEO’s: (i) conviction of, or plea of guilty or no contest to, any felony or any crime involving fraud, dishonesty or moral turpitude; (ii) engagement in gross misconduct that causes material financial or reputation harm to the Company; (iii) repeated failure to substantially perform his or her duties and responsibilities to the Company; (iv) material violation of any contract or agreement between the executive and the Company or any written Company policy or (v) disqualification or bar by any governmental or self-regulatory authority from serving in the capacity required by the executive’s job description, or loss of any governmental or self-regulatory license that is reasonably necessary for the executive to perform his or her duties or responsibilities.

“Good reason” generally means, in the absence of the NEO’s written consent: (i) any material and adverse change in the executive’s position or authority with the Company; (ii) the transfer of the NEO’s primary work site to a new location that is more than 50 miles from that in effect immediately prior to such transfer; (iii) a diminution of the NEO’s base salary by more than 10%, unless such diminution applies to all other senior executives or (iv) a material breach of the employment agreement by the Company or our Bank.

“Change in control” generally means the occurrence of any of the following events: (i) during any period of less than 36 months, individuals who constitute the Board as of the beginning of the period (which we refer to as the incumbent directors) cease to constitute at least a majority of the Board; (ii) any person is or becomes a beneficial owner, directly or indirectly, of 30% or more of the combined voting power of Great Western’sthe Company’s then-outstanding securities eligible to vote for the election of the Board; (iii) the consummation of a merger, consolidation, statutory share exchange or similar form of corporate transaction involving the Company that requires the approval of the Company’s stockholders (generally excluding such an event with NAB or any of its subsidiaries);stockholders; (iv) the consummation of a sale of all or substantially all of the Company’s assets (other than to NAB or any of its subsidiaries) or (v) the Company’s stockholders approve a plan of complete liquidation or dissolution of Great Western.the Company.

Each employment agreement also contains confidentiality and non-disparagement provisions, which apply indefinitely, and non-competition as well as client and employee non-solicitation provisions that apply during the term of the employment agreement and for one year following a termination of employment for any reason.