Chris Hemsworth shared a sweet tribute to his Avengers co-star Robert Downey Jr on Monday, as the American actor celebrated turning 56 on Sunday overseas.

The Thor star, 37, shared a series of throwback photos behind the scenes of films the pair have worked on together over the years.

‘Happy birthday to this very special human!’ Chris captioned the post on Instagram.

‘Happy birthday to this very special human!’: Chris Hemsworth (right) shared a sweet tribute to his Avengers co-star Robert Downey Jr (left) as he celebrated his 56th birthday on Sunday

‘Thanks to his mind blowing creativity and unrivalled leadership we were all able to ride on his coattails through the marvel cinematic universe forever grateful. Love ya mate @robertdowneyjr.’

In one photograph, Chris wore sunglasses as he posed alongside Robert on the set of a film.

The Hollywood stars also made a funny face as they both posed for another selfie.

Tribute: He shared a series of photos to Instagram and wrote: ‘Happy birthday to this very special human! Thanks to his mind blowing creativity and unrivalled leadership we were all able to ride on his coattails through the marvel cinematic universe forever grateful. Love ya mate’

It comes as Chris and his wife Elsa are both filming new movies in Sydney.

The power couple travel back home to Byron Bay on weekends, where they built a $30million mansion.

Chris has been working on new marvel film Thor: Love and Thunder in Sydney and is also rumoured to be producing Elsa’s forthcoming film, Interceptor.

New roles: Chris and his wife Elsa (pictured) are both filming new movies in Sydney and travel back home to Byron Bay on weekends

Last week, Elsa and Chris enjoyed a night at the footy, cheering on Russell Crowe’s beloved Rabbitohs.

At the game, where the Sydney Rabbitohs battled the Sydney Roosters, the couple joined the likes of Isla Fisher, Natalie Portman and Jeff Goldblum in a private box.

Also in the box were the likes of Thor: Love and Thunder director Taika Waititi, actress Tessa Thompson and Idris Elba’s wife, Sabrina Dhowre Elba.