An Ironman triathlon is a triathlon sanctioned by the World Triathlon Corporation that adheres to specific distances for each part of the event. The Ironman World Championship is an annual triathlon race, possibly the most famous triathlon in the world. It is held in the US state of Hawaii. It features three endurance events: swimming, biking, and running. It is based in Kailua-Kona, Hawaii and involves a 2.4 mile (3.86 kilometre) swim (across Kailua-Kona Bay), followed by a 112 mile (180.2 kilometre) bike ride (from Keauhou to Hawi and back), and a 26.2 mile (42.2 kilometre) marathon along the coast of the Big Island (from Keauhou to Keahole Point to Kailua-Kona).
Official qualifying events for the Hawaii Ironman take place annually around the world, in places such as Australia, Canada, the United States, Japan, the Canary Islands (Spain), South Africa, and Europe.
Many people refer to all triathlons of this length as "Ironman" races, but this is technically incorrect. Race directors are careful to use generic terms, such as Iron Distance Triathlon, to describe races that are not affiliated with the World Triathlon Corporation. The World Triathlon Corporation enforces its trademarks vigorously, including monitoring their use in the media and on the Internet. "Ironman Triathlon", "Ironman Triathlon World Championship", "MDOT" and "Swim 2.4 miles! Bike 112 miles! Run 26.2 miles! Brag for the rest of your life" are trademarks of the World Triathlon Corporation, registered in the United States and other countries.