A standard Olympic relay team has four runners. In the familiar 4×100-metre and 4×400-metre relays, each athlete runs one leg before handing the baton to the next teammate.
The 4×100-metre relay covers one lap of the track, with each runner completing 100 metres. Runners stay in assigned lanes, and the baton must be exchanged inside the designated takeover zone. A clean, well-timed exchange can matter as much as raw sprinting speed.
The number four is also built into the event’s name: “4×100” means four legs of 100 metres, while “4×400” means four legs of 400 metres. Teams may list substitutes or use different athletes in heats and finals, but only four runners compete for a team in a given race.
A common mix-up is confusing the number of runners with the number of athletes a country may enter or reserve. Those roster rules can vary by competition; the racing team itself still consists of four runners.