| Auto-Cycle Union | |
| Sport | Motorcycling |
| Formation date | 1903 |
| Affiliation | Fédération Internationale de Motocyclisme |
| Affiliation date | 1904 |
| Official website | |
| www.acu.org.uk | |
The Auto-Cycle Union (ACU Motorcycling GB) is governing body of motorcycle sport in Great Britain (not Northern Ireland, which is governed by the MCUI, the All Ireland governing body, but including the Channel Islands and the Isle of Man). Founded in 1903 and acquiring its current name in 1907 its aim was to develop motor sport through clubs and arrange touring facilities for members. In 1904 it was a founding member of the Fédération Internationale de Motocyclisme.
The 1911 Isle of Man TT was the first TT races to be organised by the ACU.
The sports covered in addition to non competitive motorcycling interests are: Grass Track (Track Racing), Enduro, Motocross, Road racing, Speedway and Trials.
The ACU also govern the safety standards for personal protection equipment worn during racing. Only motorcycle helmets which meet ACU standards and display the appropriate ACU sticker can be worn in "speed" competition. The majority of quality helmets sold in the UK now feature an ACU Gold sticker and many riders choose these for every day use in preference to those that meet the more basic BS6658:1985 legal requirement .