A Triathlon is an athletic event made up of three contests (from the Greek). Nowadays, the name triathlon is mostly applied to a combination of swimming, cycling and running.

This form of triathlon was first held by the San Diego Track Club in the 1970s. The first major triathlon event, the Ironman Triathlon, was organized in 1978 and held in Hawaii.

The International Triathlon Union (ITU) was founded in 1989.

The sport made its debut on the Olympic program in 2000.

There are a number of standard triathlon race distances, including

Though there can be some variation in race distances, the standards to which most race directors conform are those given above.

Triathlon is also the name of a Marvel Comics super-hero, belonging to The Avengers.