Tennis superstar Serena Williams and Olympic champion Usain Bolt have joined a team of high profile investors backing sports startup Let's Do This.

Launched in 2016, the online tool offers people the opportunity to book themselves into running, cycling, triathlon and obstacle races.

The company was founded by friends Alex Rose and Sam Browne, who – as passionate runners and cyclists – felt that discovering and entering events was often an arduous process.

The duo created Let's Do This to make it easier for people to "find their perfect race".

The company has now secured around US$5m worth of funding – including investments through seed accelerator Y Combinator, which helped launch the likes of Airbnb and Dropbox.

Williams and Bolt will join existing backers which include serial tech entrepreneur Pete Flint, Gmail creator Paul Buchheit, Moneysupermarket co-founder Simon Nixon and marathon world record holder Paula Radcliffe.

“I’ve seen first-hand the incredible impact these events can have on making people fitter, healthier and happier," said Serena Williams, a 22-time Grand Slam Champion.

"I love that Let’s Do This is not only making events like these more accessible but also helping to support athletes of all different fitness levels."

Usain Bolt, world record holder for 100m, 200m and 4x100m, added: “Throughout my career I’ve been lucky enough to inspire people to follow their dreams, get off the couch and get exercising.

"That’s what attracted me to Let’s Do This. It’s a company that is totally committed to changing the world and inspiring more people to get out there.”

Let's Do This currently has offices in London and San Francisco and is looking to use the funding to expand its global reach.

"We're on a mission to help more people discover epic experiences than any other community on the planet," the founders Alex Rose and Sam Browne said in a statement.

"Whether you’re looking for a 5k fun run or a double Ironman triathlon, we list more mass-participation sports events than any other website on the planet. These include running, triathlon, cycling, obstacle racing, swimming, and many others.

"We believe that the best experiences are those recommended by others. Our passionate community share their event experience by contributing reviews and photos to help others find their perfect event. Over a million people have discovered events through Let’s Do This."