Arthur J. Gallagher & Co. (AJG) is an American global insurance brokerage and risk management services firm headquartered in Rolling Meadows, Illinois (a suburb of Chicago).

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.

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.

[citation needed] In September 2023, it was announced Arthur J. Gallagher & Co., had acquired the UK-based personal lines insurance broking service, Lifesure Group Limited, for an undisclosed amount.

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

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

[17] Australia branches: Adelaide, Alice Springs, Bacchus Marsh, Ballarat, Beenleigh, Bexley, Brisbane, Cairns, Canberra, Darwin, Dubbo, East Melbourne, Hobart, Horsham, Katherine, Launceston, Mulgrave, 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, Blenheim, Christchurch, Dunedin, Greymouth, Hamilton, Invercargill, Kaitaia, Kapiti, Kerikeri, Napier, Nelson, New Plymouth, Palmerston North, Queenstown, Takapuna, Taupō, Tauranga, Whanganui, Wellington, and Whangārei.

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

[23] Caribbean branches: Antigua, Bermuda, Barbados,Trinidad and Tobago, Dominica, Grenada, Jamaica, St. Lucia, St. Vincent and the Grenadines, as well as St. Kitts and Nevis.

In December 2022, it was announced Arthur J. Gallagher & Co. had acquired the São Paulo-headquartered retail insurance broker, Interbrok Group for an undisclosed sum.