Arthur J. Gallagher & Co. (AJG) is a US-based global insurance brokerage and risk management services firm headquartered at in Rolling Meadows, Illinois (a suburb of Chicago). The firm was established in 1927 and is the third largest insurance broker in the world.

The company dates back to 1927 when Arthur James Gallagher started a brokerage firm in Illinois. The end of World War II brought his three sons, John, James, and Robert, into the business. The company incorporated in 1950 when revenues were $175,000. In 1957, the firm won Beatrice Foods Company as a client.

Despite the stiff competition in a crowded domestic market that put steady downward pressure on property and casualty premiums during the 1990s and dating back to the late 1980s, the firm was still able to record double-digit growth in all but three years from 1990 through 2000, according to Investor's Business Daily.

Gallagher's purchased 16 smaller brokerages during 2000. The firm had grown its presence to include about 50 U.S. cities.

A history and the values of the firm were documented by Robert E. Gallagher and Alison Kittrell in a book called The Gallagher Way, published in 2005 by Marketing Counsel and iUniverse.

In 2010 Gallagher Brazil was established following the company's takeover of Securitas Re of São Paulo from Estater Gestao de Investimentos Ltda.

In July 2015 the firm was ranked third in the Best's Review world's largest brokers list.

In June 2016, it was announced that Gallagher had joined the Fortune 500 for the first time. Gallagher currently ranks 462 on the list.

During the first second quarter and the first half of the year, the company improved their profitability margin and posted growth in revenue and in earnings per share. The second quarter of 2016 saw Arthur J. Gallagher & Co. (NYSE: AJG) post an overall organic growth of 3.6% with $939 million in revenue in reported GAAP. Domestically in the United States, the company saw about 3% organic growth.

Arthur J. Gallagher Asia Limited was incorporated in 2002.

Arthur J. Gallagher & Co. acquired Singapore-based ITI Solutions Pte Ltd. in 2011. ITI is a specialist insurance broker with expertise in marine cargo, political risk, trade credit risk, and specialty lines. ITI was rebranded as Gallagher Singapore.

Singapore branches: Singapore

In July 2016, Arthur J. Gallagher acquired an 85% stake in Swedish specialist insurance and reinsurance broker Brim AB. At the time of acquisition, the Scandinavian brokerage posted revenues of $11.4 million and employed under 30 people. Scandinavia is an area of strategic development for Arthur J. Gallagher and this deal bolstered their purchase of Norwegian specialty insurance broker Bergvall Marine AS in December 2013.

Between 2010 and 2012 British operations have grown in importance. In 2012 the UK was the source of 14% of company revenue - $352.3m up 137% versus 2010. The United States contributes 80% of revenue - $2,006.1m up 24%. The other 6% came from Australia, Bermuda and Canada ($161.9m up 59%).

Scotland branches: Aberdeen, Ayr, Dumfries, Dundee, Edinburgh, Fort William, Glasgow, Inverness, Kilwinning, Irvine, Newton Stewart and Stirling.

England branches: Barnstaple, Birmingham, Bordon, Bournemouth, Brierly Hill, Bristol, Brixham, Chelmsford, Chester, Chichester, Coventry, Croydon, Exeter, Feering, Gloucester, Godalming, Guildford, High Wycombe, Horsham, Ipswich, Leeds, Leicester, Liss, Liverpool, Northampton, Norwich, Nottingham, Orpington, Portsmouth, Rickmansworth, Sevenoaks, Sheffield, Southampton, St. Austell, Swindon, Talbot Green, Wakefield and Wigan

Channel Islands branches: Alderney

Northern Ireland branches: Belfast

Wales branches: Cardiff, Llantrisant, Newport, Tonyrefail and Wrexham

Other branches: Alderney (Channel Islands), St. Sampson (Guernsey), Isle of Man, Isle of Skye and in Jersey

In 2014, Arthur J. Gallagher expanded their brand proposition in Australia with the acquisition and rebranding of OAMPS Insurance Brokers.

Australia branches: Adelaide, Alice Springs, Bacchus Marsh, Ballarat, Beenleigh, Bexley, Brisbane, Cairns, Canberra, Darwin, Dubbo, Hobart, Horsham, Katherine, Launceston, Newcastle, Sydney, Perth, Shepparton, Toowoomba, Townsville, Wagga Wagga, Wangaratta, Warragul, and Wollongong.

In 2014, Arthur J. Gallagher purchased New Zealand nationwide insurance brokerage, Crombie Lockwood, New Zealand branches: Auckland, Bleinheim, Christchurch, Dunedin, Greymouth, Hamilton, Invercargill, Kaitaia, Kapiti, Kerikeri, Napier, Nelson, New Plymouth, Palmerston North, Queenstown, Takapuna, Tauranga, Wanganui, Wellington, and Whangarei.

In February 2015, Arthur J. Gallagher & Co. acquired Ottawa-based Cohen & Lord Insurance Brokers Ltd. The terms of the transaction were not disclosed.

In November 2015, the firm acquired Christie Phoenix Ltd. and their affiliate Discovery Insurance Services Ltd., both located in Victoria B.C. Christie Phoenix is a retail insurance broker founded more than 40 years ago and specializes in providing commercial property and personal lines of insurance service to middle-market and individual clients across British Columbia.

In June 2016, Arthur J. Gallagher & Co. reached a milestone in the Canadian market by rebranding Noraxis group of insurance brokers to Arthur J. Gallagher Canada Limited.

Canada branches: Calgary, Edmonton, Halifax, London, Markham, New Glasgow, Ottawa, Toronto, and Winnipeg.

In August 2017, the firm announced the acquisition of employee benefits insurance agency Ballard Benefit Works, Inc., based in Howell, Michigan.

Caribbean branches: Bermuda, Barbados, Grenada, Jamaica, St. Lucia, St. Vincent and the Grenadines, as well as St. Kitts and Nevis.

Chile branches: Santiago and Viña del Mar.

Colombia branches: Bogotá