The Auto-Cycle Union (ACU) is the governing body of motorcycle sport in the British Isles, including the Channel Islands and the Isle of Man, excluding Northern Ireland[1][2] and the Republic of Ireland.

[4][5] Its aim was to develop motor sport through clubs and arrange touring facilities for members.

From page one of the Auto-Cycle Union Official Pocket Handbook, 1964:[4] Auto Cycle Union: Founded in 1903 as a Branch of the Royal Automobile Club to protect the interests of Motorcyclists and to encourage the Sport and Pastime of Motorcycling, and since 1924 has existed solely for the purpose of encouraging and controlling the Sport.In 1904 it was a founding member of the Fédération Internationale de Motocyclisme.

[7] The ACU is currently (2020) administered from offices in Rugby, Warwickshire, UK.

[14] The ACU also governs the safety standards for personal protection equipment worn during racing.