A triathlon is an endurance race that combines three different sports in sequence: swimming, bicycling, and running. Athletes complete all three events one after another without stopping, and whoever finishes the entire course in the fastest time wins.

The most famous triathlon distance is called an Ironman, which includes a 2.4-mile swim, a 112-mile bike ride, and a 26.2-mile run (a full marathon). That's an incredibly grueling challenge that can take elite athletes 8-10 hours to complete. Most triathlons are much shorter, though. The Olympic distance triathlon features a roughly 1-mile swim, a 25-mile bike ride, and a 6-mile run. Many communities offer sprint triathlons with even shorter distances that kids and beginners can attempt.

The word comes from the Greek prefix tri- meaning “three” and athlon meaning “contest.” Triathlons test your strength and speed in each individual sport, plus your ability to transition smoothly from one to the next while your body is already tired. Athletes train for months or years to build the stamina, mental toughness, and strategic thinking needed to excel in all three disciplines.