Matt Damon didn’t realize just how much money he’d be missing out on when he turned down a role in the mega-blockbuster “Avatar”.

The actor spoke about being offered the lead role in the much-loved 2009 flick during his Cannes Film Festival masterclass on Friday.

According to Deadline, Damon explained how director James Cameron offered him 10 per cent of the movie’s profits. It went on to gross $2.8 billion globally.

“I was offered a little movie called ‘Avatar’, James Cameron offered me 10 per cent of it,” Damon recalled. “I will go down in history… you will never meet an actor who turned down more money.”

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The star turned down the role, which ended up going to Sam Worthington, because he was shooting the Jason Bourne movies.

Damon also spoke about the first time he told John Krasinski his “Avatar” story, with “The Office” actor replying: “Nothing would be different in your life if you had done ‘Avatar’, except you and me would be having this conversation in space.”

Damon joked of the upcoming “Avatar” flicks, “There’s sequels? Oh my god.”

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Damon is in Cannes premiering his new movie “Stillwater”, in which he plays a Donald Trump supporter.

The synopsis for the movie reads, “An American oil-rig roughneck travels to Marseille, France, to visit his estranged daughter, in prison for a murder she claims she didn’t commit. Confronted with language barriers, cultural differences and a complicated legal system, he soon builds a new life for himself as he makes it his personal mission to exonerate her.”

Damon said of his character, Bill Baker, during Friday’s press conference, “He is who he is and he’s from where he’s from, and the movie has a lot of empathy for him, and so do we.

“These guys don’t apologize for who they are or what they believe. ‘Do you own a gun? Yeah, I’ve got two,’” he added.

Damon and director Tom McCarthy shared how they spent a good amount of time in Oklahoma meeting with the “roughnecks” of the film who spend hours driving from oil rig to oil rig before heading home.

“We got so much guidance from the actual guys,” Damon revealed. “It’s a culturally very specific place, and a very different place from how he and I grew up. These people were wonderful to us, and really helped us. I didn’t know when I first read the script how specific this culture was in Texas and Oklahoma.”