An individual time trial (ITT) is a road bicycle race in which cyclists race alone against the clock on flat or rolling terrain, or up a mountain road such as Alpe d'Huez (in French: contre la montre – literally "against the watch", in Italian: tappa a cronometro "stopwatch stage"). There are also track-based time trials where riders compete in velodromes, and team time trials (TTT). ITTs are also referred to as "the race of truth", as winning depends only on each rider's strength and endurance, and not on help provided by team-mates and others riding ahead and creating a slipstream. The opening stage of stage race will often be a short individual time trial called a prologue.

Starting times are at equal intervals, usually one or two minutes apart. The starting sequence is usually based on the finishing times in preceding races (or preceding stages in the case of a multi-stage race) with the highest ranked cyclist starting last. Starting later gives the racer the advantage of knowing what time they need to beat (and also makes the event more interesting to spectators). Competitors are not permitted to draft (ride in the slipstream) behind each other. Any help between riders is forbidden. The rider with the fastest time is declared the winner.

In many racing sports an athlete (or occasionally a team of athletes) will compete in a time trial against the clock to secure the fastest time. In cycling, for example, a time trial (TT) can be a single track cycling event, or an individual or team time trial on the road, and either or both of the latter may form components of multi-day stage races. In contrast to other types of races, athletes race alone since they are sent out in intervals (interval starts), as opposed to a mass start.

In cross country skiing and biathlon competitions, skiers are sent out in 30 to 60 second intervals.

In rowing, time trial races, where the boats are sent out at 10 to 20 second intervals, are usually called "head races."

In many forms of motorsport, a similar format is used in qualifying to determine the starting order for the main event, though multiple attempts to set the fastest time are often allowed. In rallying, the special stages are run in a time-trial format. A similar race against the clock or time attack is often part of racing video games.