The world of professional triathlon is primarily split into three circuits:
- The "short course", or Olympic-distance competitive circuit, run by the International Triathlon Union (ITU), which includes the ITU World Cup series and ITU World Championships. In 2004, the ITU World Cup included over 75 different events.
- The "long course", or "Ironman" circuit, run by the World Triathlon Corporation (WTC), which culminates each year with the Hawaii Ironman World Championship. These races are not recognised as "official" by the ITU, but are unquestionably the best-known series of races in the sport.
- The XTerra off-road triathlon championship series.
In addition, the ITU has a Long Distance Triathlon series, with races slightly shorter (except for the swim) than the Ironman standard. This circuit is a new addition, with four annual events as of 2005. Many of the same athletes compete in Ironman and ITU Long Distance races.
The term Ironman Triathlon is a trademark of the World Triathlon Corporation and refers to the series of races organised by the WTC. Races of this distance which are not organised by the WTC are commonly referred to as Iron Distance Triathlon.
