World Triathlon, previously known as the International Triathlon Union (ITU), is the international governing body for the multi-sport disciplines of triathlon, duathlon, aquathlon and other nonstandard variations. It is recognised as the international federation for the sport of triathlon and its derivatives by the International Olympic Committee, and it organises Olympic triathlon events on behalf of the IOC.

In addition to regulating and setting the rules of the sport, World Triathlon organises the top level international race series the World Triathlon Championship Series and the ITU Triathlon World Cup. World Triathlon also has a long-distance race circuit with official world championships, while in 2024 it will begin to sanction and recognise a World Championship Tour of Long-Distance Triathlon organised by the Professional Triathletes Organisation. World Triathlon does not have an official relationship with the other three major commercial triathlon circuits, Ironman Triathlon, XTERRA Triathlon or Super League Triathlon.

Additionally, World Triathlon regulated, sanctions and organizes official sprint distance and team relay triathlon championships, as wel as Aquathlon (run-swim-run), Duathlon (run-bike-run) and Winter triathlon championships.

World Triathlon is headquartered in Lausanne, Switzerland.