Keirin (競輪 / ケイリン?, [keiɽiɴ]) "racing wheels" is a form of motor-paced cycle racing in which track cyclists sprint for victory following a speed-controlled start behind a motorized or non-motorized pacer. It was developed in Japan around 1948 for gambling purposes and became an official event at the 2000 Olympics in Sydney, Australia.

Races are about 2 kilometers long: 8 laps on a 250 m track, 6 laps on a 333 m track, 5 laps on a 400 m track. Lots are drawn to determine starting positions for the sprint riders behind the pacer, which is usually a motorcycle, but can be a derny or tandem bicycle. Riders must remain behind the pacer for a predetermined number of laps. Initially it makes circuits at about 25 kilometres per hour (16 mph), gradually increasing to about 50 kilometres per hour (31 mph). The pacer usually leaves the track approximately 600–700 meters before the end. The winner's finishing speed is around 70 kilometres per hour (43 mph).

Competition keirins are often conducted over several rounds with one final. Sometimes eliminated cyclists get the opportunity to try again in the repechages.