Mark Allen (born January 12, 1958, in Glendale, California) is an American triathlete and six-time Ironman Triathlon World Champion.

[1] After competing and losing in the Ironman Triathlon Championships six times (often to Dave Scott), Allen emerged victorious in 1989, winning one of the most difficult one-day sporting events in the world.

This was the first of six Ironman victories for Allen, the last coming in 1995 at age 37, making him the oldest winner of the event at that time.

He has also excelled at the Olympic distance, winning the sport's inaugural World Championships in 1989 in Avignon, France,[2] by more than a minute.

21 stands for his two season run of 21 straight victories, along the way defeating every one of the top 50 triathletes in the world.