A middleweight Olympic gold medallist from both London 2012 and Rio 2016 and two time world champion, Shields has signed an exclusive, multi-year deal with PFL.

She will not take part in the season format in 2021, where fighters compete regularly throughout the year, but will look to join that format in 2022.

Shields is expected to have two bouts in 2021, while continuing to box this year too.

"I wanted to test myself," said Shields to ESPN.

"I want to see if I can be a world champion in boxing and a world champion in MMA.

"I'm not saying boxing is easy, but I've been on top of the world for almost 14 years now."

At London 2012, she defeated Nadezhda Torlopova of Russia in the middleweight final and then defeated The Netherlands' Nouchka Fontijn at the Rio 2016 Games.

The 25-year-old has flirted with the idea of moving to MMA in the past, previously challenging two-weight Ultimate Fighting Championship (UFC) champion Amanda Nunes to a two-fight contest - one boxing match and one MMA match.

So far, she has attended some jiu-jitsu classes and has worked with US Olympic wrestler Adeline Gray too.

The PFL season is expected to start again in April in Las Vegas following the postponement of the 2020 season.

Once involved in the promotion, she could compete against two-time Olympic judo champion Kayla Harrison, who won the women's lightweight division title in 2019 and currently has an 8-0 record in MMA.

Many Olympians have moved into MMA following careers in sports like boxing, wrestling and judo.

This includes judo bronze medallist and professional wrestler Ronda Rousey, who became the first woman to be inducted to the UFC Hall of Fame.

Another retired MMA star of a similar stature, Daniel Cormier, won world bronze in freestyle wrestling and competed for the US at Athens 2004 in the sport before becoming a light heavyweight and heavyweight UFC champion at the same time.

Shields also holds a 10-0 record in professional boxing.