The track cycling gold medalist from the Beijing Olympics, who also rowed to silver in 2004 in Athens, will compete in Ironman U.K. on July 22, 2012.
Facing stiff competition to make the grade for London 2012, 31-year-old Rebecca Romero left the Great Britain cycling team last Autumn.
She started her professional sporting career as a rower in 1998, winning gold at the Under-23 world champs before finding the podium as part of the silver medal-winning quadruple scull team in Athens.
Suffering disc problems in her back, she switched sports to successfully race the 3km time trial in China as part of Dave Brailsford all-conquering British cycling squad.
Romero was awarded an MBE in 2009 for her achievements.
Speaking about her switch to an ultra-endurance event that is likely to last for over nine hours, she said: “It’s the most iconic endurance event there is.
“I don’t just want to do a triathlon, I want to be part of a great epic event.”
Read more: Thesun.co.uk