On September 25, 1974, the first modern triathlon event was held in San Diego, sponsored by the San Diego Track Club. Prior to this, other three-sport events existed but did not feature the swim-bike-run combination. The first triathlon included a 6-mile run, a 5-mile cycle and a 500-yard swim. In 1978, The Hawaii Ironman Triathlon® debuted with a 2.4-mile open-water swim, a 112-mile bike race and a 26.2-mile marathon run.

In the 2000 Sydney Olympics, the triathlon made its first appearance in the games with a 1,500-meter swim, a 40-kilometer cycle and 10 km run. Today, triathlon races feature a variety of distances, from kid-friendly races to ultra-endurance events.