A new T100 race series for longer-distance triathlon has been launched, with eight star-studded 100km races featuring a prize pot that looks certain to tempt the best of Ironman and Olympic-distance athletes.

Jointly launched by the Professional Triathletes Organisation (PTO) and governing body World Triathlon, the T100 will feature races comprising a 2km swim, 80km bike and 18km run that will last around a TV-friendly three hours.

Among those already signed are Australian women's world No.2 Ashleigh Gentle and men's world No.16 Aaron Royle.

Initially an eight-race program, the T100 will kick off in Miami in March, before moving to Singapore, California, London, Ibiza, Las Vegas and Dubai.

It will culminate in a November grand final in a Middle East venue to be decided.

Each race will have a $US250,000 ($A380,000) prize fund, including $US25,000 for the winner.

The overall men's and women's winners will collect $US210,000 from an additional total prize pool of $US2 million.

With athlete contracts and T100 Triathlon World Tour pool added into the mix, the series will offer more than $US7 million ($A11 million) in compensation - huge money for the sport.

The new event marks a notable collaboration between the two organisations as World Triathlon previously had little involvement with long-distance racing, which is dominated by the Ironman brand.

Crucially, the series will have a consistent field, with 40 of the world's leading long-distance athletes signed up and committed to compete in a minimum of five races and the grand final.

The lengths fall in between those of the Olympic triathlon (1500m swim, 40km bike, 10km run) and the Ironman world championship (3.5km, 180km, 42km).

Britain's double Olympic champion Alistair Brownlee has joined the new venture, saying he was excited about the event partly because of the unknown factor as athletes have not yet learned how to nail the pacing.

"I want to see more people watching top level long-distance triathlon, being inspired by seeing the top athletes racing," he said.

In keeping with triathlon tradition, the events will also feature large-scale amateur age group races.

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