False start

In sports, a false start is a disallowed start, usually due to a movement by a participant before (or in some cases after) being signaled or otherwise permitted by the rules to start. Depending on the sport and the event, a false start can result in a penalty against the athlete's or team's field position, a warning that a subsequent false start will result in disqualification, or immediate disqualification of the athlete from further competition.

A reduced starting lineup after Kamé Ali was disqualified due to a false start in heat 3 of the men's 110 metres hurdles at the 2012 London Olympics

False starts are common in racing sports (such as swimming, track, sprinting, and motor sports), where differences are made by fractions of a second and where anxiety to get the best start plays a role in the athletes' behavior.

A race that is started without a false start is referred to as a fair start or clean start.