As triathlon continued to grow in popularity, official rules committees began to form. Today, there are multiple governing bodies for the sport of triathlon, each sanctioning and supporting different length races. The most prominent of which are USA Triathlon (USAT), The International Triathlon Union (ITU), and the World Triathlon Corporation (WTC), which licenses the Ironman series of races.

USA Triathlon (USAT)

USA Triathlon (USAT) is the national governing body for triathlon, duathlon, aquathlon and winter triathlon, of which it sanctions more than 2000 races each year. The USAT formed in 1982 when the U.S. Triathlon Association and the American Triathlon Association merged. Original membership was only about 1500. In just 25 years, membership has grown to more than 100,000 making it the largest multisport organization in the world.

International Triathlon Union (ITU)

The International Triathlon Union (ITU) was founded in 1989 in Avignon, France, the site of the first official world championships. The primary race of the ITU is the Olympic distance race. The ITU sanctions and organizes a World Cup series of these races every year, culminating in an annual World Championship for elite pro-triathletes, junior pro-triathletes and amateur athletes in 5-year age-groups.
World Triathlon Corporation (WTC)

The World Triathlon Corporation (WTC) was founded in 1990 and organizes, licenses, and promotes the Ironman Triathlon Series, culminating each year with the Hawaii Ironman Triathlon World Championships. Although the Ironman races are not recognized by the ITU as official world championships, the Hawaii Ironman race is considered by most to be the most prestigious event in the world.