Michelle Bridges has baby boy

Celebrity fitness trainers Michelle Bridges and Steve 'Commando' Willis have welcomed their first child together - a boy named Axel Bridges Willis.

Celebrity fitness couple Michelle Bridges and Steve Willis have welcomed their first child together. (AAP)

Celebrity fitness trainers Michelle Bridges and Steve "Commando" Willis have confirmed the arrival of their first child together, and it's a boy.

"We are thrilled to welcome our little boy into the world, Axel Bridges Willis born 19/12/15," Bridges announced on Tuesday via Instagram.

Bridges said Axel is "healthy and happy".

The announcement was immediately met with well wishers from fans of their TV show, The Biggest Loser.