Six-day cycling is a track cycling event that competes over six days. Six-day races started in Britain, spread to many regions of the world, were brought to their modern style in the United States and are now mainly a European event. Initially, individuals competed alone, the winner being the individual who completed the most laps. However, the format was changed to allow teams (usually of two riders each), one rider racing while the other rested. The 24-hours a day regime has also been relaxed, so that most six-day races involve six nights of racing, typically from 6pm to 2am, on indoor tracks (velodromes). Six-day events are annually hosted in London, Berlin, Ghent, Copenhagen, Hong Kong, Manchester, Melbourne and Brisbane.

The overall winner is the team which completes most laps. In the event of teams completing the same number of laps, the winner is the team with most points won in intermediate competitions (see points race). As well as the 'chase' to gain laps over competitors, a typical six-day programme will include time trials, motor-paced, intermediate sprint and elimination races. In the main 'chase' or madison events (so-called after Madison Square Garden in New York City, where the two-man format was devised), both riders may be on the track at the same time, taking it in turns to race, hand-slinging each other back into action.