The Fire Brigades Union or FBU is the British Trades Union that represents 50,000 or so firemen employed by local authority fire brigades in the United Kingdom. (But only the rank and file; their superiors have the Fire Officers Association and the Association of Principal Fire Officers to look after their interests.)
The Union was formed in 1918 as the Firemen's Trade Union but changed to its current name to avoid confusion with the other sort of Locomotive Firemen who lit fires rather than put them out.