2024 Proxy Statement

Message To Our Stockholders

We had another outstanding year in 2023. On a combined basis, our core brokerage and risk management segments produced adjusted revenue1 growth of 18.7% (to $9.9 billion) and adjusted EBITDAC1 growth of 20.5% (to $3.2 billion). We achieved organic revenue growth of 9.8% in our core brokerage and risk management segments.

Dear Fellow Stockholder,

March 22, 2024

On behalf of our Board of Directors, I invite you to attend our 2024 Annual Meeting of Stockholders. We will be conducting our Annual Meeting virtually again this year. If you are not able to attend, we encourage you to vote by proxy. These proxy materials contain detailed information about the matters on which we are asking you to vote. We hope you will read these materials and then vote in accordance with the Board's recommendations. Your vote is very important to us.

Financial Performance. We had another outstanding year in 2023. On a combined basis, our core brokerage and risk management segments produced adjusted revenue1 growth of 18.7% (to $9.9 billion) and adjusted EBITDAC1 growth of 20.5% (to $3.2 billion). We achieved organic revenue growth of 9.8% in our core brokerage and risk management segments. We completed acquisitions representing $885.1 million in estimated annualized revenue and made significant progress integrating the Wills Re and Buck acquisitions. It was truly a fantastic year for our franchise, and I am excited about our future.

Board of Directors. Our Board of Directors is comprised of a group of committed and highly qualified individuals who care deeply about our company and bring a diversity of experiences and perspectives to our Board deliberations. Our directors' diverse professional backgrounds, skill sets and independent thought leadership have been invaluable to me and the management team in establishing our long-term business strategy, executing on that strategy and managing both short- and long-term risks facing the company.

After 18 years of service, William Bax is retiring from the Board and not standing for re-election at this year's meeting. Bill served as Chairman of the Audit Committee for many years and most recently served as Chairman of the Risk and Compliance Committee. During Bill's tenure we grew from $1.5 billion in revenue and 8,750 employees to $9.9 billion in revenue and 52,000 employees. Bill contributed significantly to these results and I want to personally express my appreciation for his years of dedicated service and contributions to our financial success.

I am excited to introduce a new director nominee, Deborah Caplan. I encourage you to review her qualifications and support her and all of our nominees. Including Ms. Caplan, we have added three new independent directors to our Board since 2020, a reflection of our continuing commitment to disciplined board refreshment.

1 See Exhibit A for reconciliations of non-GAAP measures.

Commitment to Stockholder Engagement. Our Board values the feedback and insights gained from our engagement with stockholders. During the past year, in addition to our regular discussions with stockholders regarding our financial results, we engaged with stockholders representing more than 50% of shares outstanding on corporate governance, broader sustainability matters and executive compensation. We are committed to including our stockholders' perspectives in our deliberations and we believe that regular communication is necessary in order to ensure thoughtful and informed consideration of evolving best practices in areas of concefor our stockholders.

Our Unique Culture. For nearly a century, we have proudly built a reputation of trust and integrity with our clients and colleagues. Now, more than ever, I believe that this culture and history of integrity is a true competitive advantage and a key differentiator when recruiting and retaining talent, attracting acquisition partners, retaining our valued clients and winning new business.

Looking Ahead. During the course of 2023, clients added exposures and coverages to their existing insurance programs, payrolls and covered lives increased, demand for our benefits consulting services remained strong, and we experienced growth in claim counts within our claims handling business. We believe increases in property/casualty rates will continue throughout 2024 due to rising loss costs, a hard reinsurance market, increased frequency of catastrophe losses and social inflation. In addition, the combination of increasing insurable values, a tight labor market and lower unemployment will likely contribute to increases in client insured exposures. Of course, our job is to help our clients navigate these market pressures. Our team of professionals continue to deliver the very best insurance and risk management advice to clients to help them succeed in this challenging environment.

On behalf of our Board of Directors, thank you for your continued support. We look forward to welcoming you at our 2024 Annual Meeting.

Sincerely,

J. Patrick Gallagher, Jr.

Chairman of the Board and

Chief Executive Officer

Arthur J. Gallagher & Co.

2850 Golf Road

Rolling Meadows, Illinois 60008-4050

Notice of 2024 Annual Meeting of Stockholders

Dear Stockholder:

We are pleased to invite you to the 2024 Annual Meeting of Stockholders of Arthur J. Gallagher & Co. (Gallagher or the company), which will be held as a virtual meeting, conducted via live audio webcast, on May 7, 2024, at 9:00 AM CDT. At the meeting, stockholders will vote on each item described below and we will transact such other business that properly comes before the meeting.

Voting Items

Board Recommendations

• Elect each of the 9 nominees named in the accompanying Proxy Statement as directors to	FOR each nominee
	hold office until our 2025 Annual Meeting (Item 1)
•	Ratify the appointment of Ernst & Young LLP as our independent registered public	FOR
	accounting firm for the fiscal year ending December 31, 2024 (Item 2)
•	Approve, on an advisory basis, the compensation of our named executive officers (Item 3)	FOR

Stockholders of record at the close of business on March 18, 2024 are entitled to notice of and to vote at the Annual Meeting. The applicable voting standard and the treatment of abstentions and "broker non-votes" for each of these items are set forth on page 48 of the Proxy Statement. Stockholders may vote shares prior to the meeting by visiting www.proxyvote.com.

On the day of the Annual Meeting, stockholders of record as of the close of business on March 18, 2024, the record date, are entitled to participate in and vote at the Annual Meeting. To participate in the Annual Meeting, including to vote and ask questions, stockholders of record should go to the meeting website at www.virtualshareholdermeeting.com/AJG2024, enter the 16-digit control number found on your proxy card or Notice of Internet Availability of Proxy Materials, and follow the instructions on the website. If your shares are held in street name and your voting instruction form or Notice of Internet Availability of Proxy Materials indicates that you may vote those shares through the www.proxyvote.com website, then you may access, participate in, and vote at the Annual Meeting with the 16-digit access code indicated on that voting instruction form or Notice of Internet Availability of Proxy Materials. Otherwise, stockholders who hold their shares in street name should contact their bank, broker or other nominee (preferably at least 5 days before the Annual Meeting) and obtain a "legal proxy" in order to be able to attend, participate in or vote at the Annual Meeting.

Stockholders are encouraged to log in to the Annual Meeting website before the Annual Meeting begins. Online check-in will be available approximately 10 minutes before the meeting starts. Additional information regarding the rules and procedures for participating in the virtual Annual Meeting will be set forth in our meeting rules of conduct, which stockholders will be able to view during the meeting.

We urge you to read the Proxy Statement for additional information concerning the matters to be considered at the Annual Meeting and then vote in accordance with the Board's recommendations. Your vote is very important to us.

By Order of the Board of Directors

WALTER D. BAY

GENERAL COUNSEL AND SECRETARY

March 22, 2024

Important Notice Regarding the Availability of Proxy Materials for the Annual Meeting of Stockholders

to Be Held on May 7, 2024:

We are making this Notice of Annual Meeting, this Proxy Statement, our 2023 Annual Report, and the Notice of Internet Availability of Proxy Materials available on the Internet at www.materials.proxyvote.com/363576 and mailing copies of these proxy materials to certain stockholders on or about March 22, 2024.

Proxy Statement
Table of Contents
Corporate Governance	1
Item 1- Election of Directors	1
Key Governance Practices	8
Board Leadership Structure	8
Director Independence	9
Compensation Committee Interlocks and
Insider Participation	9
Stockholder Views	9
Board's Role in Risk Oversight	9
Sustainability Oversight and Activities	12
Other Board Matters	13
Director Compensation	14
Certain Relationships and Related Person Transactions	15
Security Ownership by Certain Beneficial Owners and
Management	16
Equity Compensation Plan Information	18
Audit Matters	19
Item 2- Ratification of Appointment of Independent Auditor.19
Audit Committee Report	20
Executive Compensation	21
Compensation Discussion and Analysis	21
Overview of Our Executive Compensation Program	22
2023 Compensation	24
CompensationDecision-MakingProcess	30
Comparative Market Assessment	31
Compensation Committee Report	32
Executive Compensation Tables	33
Item 3 - Advisory Vote to Approve the Compensation of Our
Named Executive Officers	42
Pay versus Performance	43
CEO Pay Ratio Disclosure	47
Questions and Answers About the Annual Meeting	48
Exhibits	A-1
Exhibit A: Information RegardingNon-GAAPMeasures	A-1
Exhibit B: Resources	B-1

FREQUENTLY REFERENCED

TOPICS

Board Diversity

Director Qualifications

Board Skills and

Experience

Key Governance Practices

Board's Role in Risk

Oversight

Sustainability Oversight and Activities

Compensation Discussion and Analysis

Key Executive Compensation Practices

2023 Summary Compensation Table

Some of the statements in this proxy statement, including those related to our interim goal of 50% reduction in Scope 1 and Scope 2 carbon emissions on a per-employee basis by 2030 in addition to our goal of achieving net zero carbon emissions for our direct operations (Scope 1 and Scope 2) by 2050, may be considered forward-looking statements as defined in the Private Securities Litigation Reform Act of 1995. We caution investors that these forward-looking statements are not guarantees of future performance, and are subject to certain risks and uncertainties that could cause actual results to differ materially. Factors that could cause our future performance and actual results or outcomes to differ, possibly materially, from those expressed in the forward-looking statements include, but are not limited to, our ability to formulate and implement plans to reduce our Scope 1 and 2 carbon emissions as anticipated; our reliance on third parties, whose actions are outside our control; and the lack of widely accepted standards for measuring carbon emissions associated with insurance and resinsurance brokerage, consulting and claims managements activities, as well as other factors discussed in our 2023 Annual Report on Form 10-K, subsequent Quarterly Reports on Forms 10- Q, and the other filings we make with the Securities and Exchange Commission. Accordingly, you should not place undue reliance on forward- looking statements, which speak only as of, and are based on information available to us on, the date of the applicable document. We do not undertake any obligation to update any forward-looking statements made in or release publicly any revisions to these forward-looking statements to reflect events or circumstances after the date of this proxy statement, which speaks as of the date issued, or to reflect new information, future or unexpected events or otherwise, except as required by applicable law or regulation. The inclusion of forward-looking and other sustainability- related statements in this proxy statement is not an indication that these contents are necessarily material to investors or required to be disclosed in our filings with the SEC. In addition, historical, current and forward-lookingsustainability-related statements may be used based on standards for measuring progress that are still developing, internal controls and processes that continue to evolve, and assumptions that are subject to change in the future.

Item 1 - Election of Directors

Corporate Governance

ITEM 1 - Election of Directors

Evaluation Process for Director Candidates

The Nominating/Governance Committee considers director candidates suggested by stockholders, management or other members of the Board of Directors (Board) and may hire consultants or search firms to help identify and evaluate potential director candidates. In some cases, nominees have been individuals known to Board members or others. In the case of Deborah Caplan, one of our independent directors initially identified her as a potential director nominee. Prior to her nomination, Ms. Caplan met separately with the Chairman and CEO and each member of the Nominating/Governance Committee (which includes our Independent Lead Director), who considered her candidacy. After review and discussion, the Nominating/Governance Committee recommended, and the Board approved, Ms. Caplan's nomination at the annual meeting. For information regarding how stockholders can submit a director candidate for consideration by the Nominating/Governance Committee, as well as for information regarding "proxy access," see page 50.

The Nominating/Governance Committee evaluates director candidates by considering their judgment, qualifications, attributes, skills, integrity, gender, racial/ethnic diversity, international business or other experience relevant to our global activities and other factors it deems appropriate. The Committee looks for candidates who are leaders in the organizations with which they are affiliated and have experience in positions with a high degree of responsibility. The Committee seeks candidates free from relationships or conflicts of interest that could interfere with the director's duties to Gallagher or our stockholders. The Committee also evaluates candidates' independence and takes into account applicable requirements under Securities and Exchange Commission (SEC) rules and New York Stock Exchange (NYSE) listing standards.

Board Diversity

Our Board nominees reflect diversity of gender, race/ethnicity, tenure, nationality, age, professional background and viewpoints. Of our nine director nominees, three are women and two are racially/ethnically diverse. We are committed to maintaining a diverse and inclusive Board. Our Board has adopted the "Rooney Rule" for director searches. Under this policy, our Governance Guidelines provide that, when recruiting director candidates, the Nominating/Governance Committee includes, and requests that any search firm it engages include, qualified women and racially/ethnically diverse persons in the pool from which new director nominees are chosen. The Committee actively seeks Board members from diverse backgrounds who combine a broad spectrum of experience and expertise with a reputation for integrity. The Committee assesses the effectiveness of the Board's diversity search policy as part of its annual review process.

Board Nominees and Vote Required

Upon the recommendation of the Nominating/Governance Committee, the Board has nominated our Chairman and Chief Executive Officer (CEO) and each of the additional eight individuals listed below to hold office until the next annual meeting and the election and qualification of their successors or, if earlier, until their resignation, death or removal. Other than Ms. Caplan, each of the nominees currently serves on the Board, and all of the nominees have consented to serve on the Board if elected. If any nominee should become unable or unwilling to serve, the Board may nominate another person to stand for election or reduce the size of the Board. William Bax, a current director, is retiring from the Board and is not standing for re-election.

Each director nominee who receives more "FOR" votes than "AGAINST" votes at the Annual Meeting will be elected. Abstentions will have the same effect as a vote "AGAINST." Any incumbent director nominee who receives a greater number of votes "AGAINST" election than votes "FOR" election is required to tender an offer of resignation for consideration by the Nominating/Governance Committee in accordance with our Governance Guidelines.

2024 PROXY STATEMENT

Item 1 - Election of Directors

Director Qualifications

We have summarized below the key qualifications and areas of experience that led our Board to conclude that each non- management director nominee is qualified to serve on our Board; however, this is not intended to be an exhaustive list of their qualifications or contributions to our Board.

		Finance /		Risk
Non-Management	CEO / COO	Capital	Change	Management /	Sales and		Insurance
Director Nominees	Experience	Markets	Management	Governance	Marketing	International	Industry	Independence
Sherry Barrat	X	X	X	X	X	X		X

Deborah Caplan	X		X	X		X		X

Teresa Clarke	X	X	X	X		X		X

John Coldman	X			X		X	X

David Johnson
(Lead Independent Director)	X		X	X	X	X		X

Chris Miskel	X		X	X	X	X		X

Ralph Nicoletti		X		X		X		X

Norman Rosenthal		X		X			X	X

These percentages include our Chairman and CEO, Pat Gallagher.

The Board recommends that you vote "FOR" the election of each of the director nominees listed below

Item 1 - Election of Directors

Age: 74

Director since: 2013

Committee Memberships:

Compensation (Chair)
Nominating/Governance

Public Company Boards: 3

Independent

Age: 61

Public Company Boards: 2

Independent

SHERRY BARRAT

Ms. Barrat's qualifications to serve on our Board and chair our Compensation Committee include her executive management, operational and financial experience, in particular her deep understanding of the financial services industry and her experience leading a global client service and sales organization. Her roles at NortheTrust, NextEra Energy and Prudential Insurance mutual funds have given her experience navigating complex and changing regulatory environments. She also has significant experience with change management, including planning and implementing a CEO succession plan as part of NextEra Energy's board.

Career Highlights

NortheTrust Corporation (1990-2012)

Global financial holding company

Vice Chairman

President, Personal Financial Serviceso Member, Management Committee

Current Public Company Boards

NextEra Energy, Inc. (1998-present)o Lead Director
o Executive Committee
o Compensation Committee
o Governance & Nominating Committee
Prudential Insurance mutual funds (2013-present)o Independent trustee or director of various funds o Vice Chair, Investment Review Committee
o Governance & Nominating Committee o Compliance Committee

DEBORAH CAPLAN

Ms. Caplan's qualifications to serve on our Board include her senior executive experience, a history of building corporate cultures founded on strong values and her extensive operational experience. Her senior executive roles at NextEra Energy, one of the largest clean energy companies in the United States, have given her valuable experience navigating a complex regulatory environment and the risks and opportunities presented by climate change. In addition, her experience as a human resources leader and member of other public company boards will enable her to contribute to sound corporate governance and executive compensation practices at the company.

Career Highlights

NextEra Energy, Inc. (2011-2024)

Electric power and clean energy company

Executive Vice President, Human Resources and Corporate Services

o Vice President and Chief Operating Officer, Florida Power & Light Company o Vice President of Integrated Supply Chain
General Electric Company (prior to 2011)

Global conglomerate

Senior Vice President of Global Operations for Vendor Financial Services, GE Capital

Other senior roles in manufacturing and product development, GE Aircraft Engines

Current Public Company Boards

Mid-AmericaApartment Communities, Inc. (2023-present)o Compensation Committee
o Nominating & Corporate Governance Committee

Previous Public Company Boards

Terminix Global Holdings, Inc. (2019-2022)o Chair, Compensation Committee
o Environmental, Health and Safety Committee

Other Board Experience

Association to Advance Collegiate Schools of Business (2019-present)o Executive Committee
o Chair, Global Business Practices Council

2024 PROXY STATEMENT

Item 1 - Election of Directors

Age: 61

Director since: 2021

Committee Memberships:

Audit
Risk and Compliance

Public Company Boards: 2

Independent

Age: 76

Director since: 2014

Committee Memberships:

Risk and Compliance

Public Company Boards: 1

TERESA CLARKE

Ms. Clarke's qualifications to serve on our Board include her extensive international and financial services expertise, particularly in the areas of corporate finance and mergers & acquisitions. In addition, her roles leading or overseeing technology companies have given her valuable experience in change management, including navigating changing regulatory environments and pivoting businesses to take advantage of new technologies.

Career Highlights

Africa.com LLC (2010-present)

Africa-related digital media content company

o Chair and Chief Executive Officer
Goldman Sachs & Co. (Prior to 2010)

Global financial services firm

Managing Director, Investment Banking

Current Public Company Boards

American Tower Corporation (2021-present)o Audit Committee

Previous Public Company Boards

Change Financial Limited (2016-2020) - Australian Stock Exchange o Board Chair
o Audit Committee
Cim Group Ltd (2016-2020) - Mauritius Stock Exchange o Corporate Governance Committee

Community Involvement

Smithsonian National Museum of African Art (2022-present)o Chair, Advisory Board

JOHN COLDMAN, OBE

Mr. Coldman's qualifications to serve on our Board include his international insurance industry knowledge, his experience within the Lloyd's and London marketplaces, his experience with public company matters and mergers and acquisitions and his significant expertise in reinsurance.

Career Highlights

The Benfield Group (1988-2008)

Reinsurance and risk intermediary company

Chairman

Managing Director

Previous Public Company Boards

Omega Insurance Holdings Limited (2010-2012) - London Stock Exchange o Chairman
Brit PLC (1996-2000) - London Stock Exchange o Chairman

Other Board Experience

Lloyd's of London (2001-2006)o Deputy Chairman
o Member of Council
Roodlane Medical Ltd. (2007-2011)o Non-Executive Chairman

Community Involvement

A U.K. citizen, Mr. Coldman was appointed an Officer of the Order of the British Empire (OBE) in the Queen's Birthday Honours List 2017, for "services to business, young people, and charity."

Item 1 - Election of Directors

Age: 72

Director since: 1986

Public Company Boards: 1

Chairman Since 2006

Age: 67

Director since: 2003

Committee Memberships:

Compensation
Nominating/Governance
Risk and Compliance

Public Company Boards: 1

Independent Lead Director since 2016

PAT GALLAGHER

Mr. Gallagher is the only member of management serving on the Board. His 50 years of experience with our company and 38 years of service on the Board, his deep knowledge of our company and the insurance industry and his extensive leadership experience greatly enhance the Board's decision making and enable Mr. Gallagher to serve as a highly effective Chairman of the Board.

Career Highlights

Arthur J. Gallagher & Co. (1974-present)o Chairman
o Chief Executive Officer
o President and Chief Operating Officer o Vice President of Operations
o Production Account Executive

Previous Public Company Boards

InnerWorkings, Inc. (2011-2019)o Compensation Committee
o Nominating/Governance Committee

Insurance Industry Affiliations

The Institutes, previously known as American Institute for Chartered Property Casualty Underwriters (2003-present)
o Board of Trustees

Community Involvement

Mr. Gallagher was granted Freedom of the City of London in 2007 by the city's Lord Mayor in recognition of his outstanding contribution to the Lloyd's insurance market and for his support of the Gallagher Lifelong Learning scholarships.

DAVID JOHNSON

Mr. Johnson's qualifications to serve on our Board and as Independent Lead Director include his knowledge of corporate governance and executive compensation best practices and his experience as a senior executive of global businesses. These roles have provided him with significant experience in change management and navigating complex regulatory environments.

Career Highlights

Aryzta AG, now Aspire Bakeries (2018-2021)

Global food business

o Non-Executive Chairman, North America o Chief Executive Officer, North America
Barry Callebaut AG (2009-2017)

Cocoa and chocolate products manufacturer

o President and Chief Executive Officer, Americas o Member, Global Executive Committee
Michael Foods, Inc. (2007-2009)

Food processor and distributor

o President, Chief Executive Officer and Board Member o Chief Operating Officer
Kraft Foods Global, Inc. (prior to 2007)

Global food and beverage company

President, Kraft Foods North Americao Member, Management Committee
o Other senior roles in marketing, strategy, operations, procurement and general management

Other Board Experience

OC Flavors, Inc. (2022-present)
Jacobs Holding AG (2018-2021)o Board of Advisors
Michael Foods, Inc. (2008-2009)

2024 PROXY STATEMENT

Item 1 - Election of Directors

Age: 49

Director since: 2020

Committee Memberships:

Nominating/Governance
(Chair)
Compensation

Public Company Boards: 1

Independent

CHRIS MISKEL

Mr. Miskel's qualifications to serve on our Board and chair our Nominating/Governance Committee include his senior executive experience, his involvement in setting strategy for large businesses such as Lilly, Baxter, Baxalta and Shire, his extensive sales and marketing experience, and his knowledge of the healthcare industry and related privacy and cybersecurity issues. His senior roles in the pharmaceutical industry have also provided him with experience navigating complex and changing regulatory environments.

Career Highlights

Versiti, Inc. (2017-present)

Blood products supply company

o President and Chief Executive Officer
Baxter / Baxalta / Shire (2013-2017) - Baxalta Incorporated spun off from Baxter International Inc. in 2015 and was acquired by Shire plc in 2016

Global healthcare and pharmaceutical companies

Head of Immunology (2015-2017)

Vice President, Plasma Strategy and New Products, Global BioTherapeutics

(2014-2015)

o Vice President, U.S. BioScience National Accounts (2013-2014)
Eli Lilly and Company (prior to 2013)

Pharmaceutical company

General Manager, Lilly Australia and New Zealando Other senior roles

Community Involvement

Butler University (2021-present)o Board of Trustees
Medical College of Wisconsin (2018-present)o Board of Directors

Age: 66

Director since: 2016

Committee Memberships:

Audit (Chair)

Public Company Boards: 1

Independent

RALPH NICOLETTI

Mr. Nicoletti's qualifications to serve on our Board and chair our Audit Committee include his experience as a senior executive of global businesses, his deep financial management expertise, capital markets experience and experience managing privacy and cybersecurity issues.

Career Highlights

The AZEK Company, Inc. (2019-2021)

Building products company

o Senior Vice President and Chief Financial Officer
Newell Brands, Inc. (2016-2018)

Global consumer goods company

o Executive Vice President and Chief Financial Officer
Tiffany & Co. (2014-2016)

Global luxury jewelry company

o Executive Vice President and Chief Financial Officer
Cigna Corporation (2011-2013)

Global healthcare and insurance company

o Chief Financial Officer
Alberto Culver, Inc. (2007-2011)

Beauty products company

o Executive Vice President and Chief Financial Officer
Kraft Foods, Inc. (prior to 2007)

Global food and beverage company

Senior Vice President of Corporate Audito Other senior financial management roles

Other Board Experience

GPA Global (2023-present)
- Chair, Audit Committee
Cooper's Hawk Winery & Restaurants (2021-present)
- Chair, Audit Committee

Attachments

Disclaimer

Arthur J.Gallagher & Co. published this content on 22 March 2024 and is solely responsible for the information contained therein. Distributed by Public, unedited and unaltered, on 22 March 2024 20:35:17 UTC.

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