It's official: <i>Avatar</i> creator James Cameron wrote the blockbuster's screenplay.

It's official: Avatar creator James Cameron wrote the blockbuster's screenplay. Photo: Steve Holland

A US judge has thrown out a copyright lawsuit against Avatar director James Cameron.

Gerald Morawski alleged he gave Cameron the idea for his blockbuster about a native tribe clashing with a mining company, insisting he even sold him art concepts that were incorporated into the 2009 movie, which grossed $US2.7 billion ($A2.61 billion) at the box office.

Cameron maintained his innocence and handed over a 45-page declaration of how he came up with the project's concept.

Judge Margaret Morrow on Tuesday ruled in Cameron's favour, stating: "Clear, undisputed evidence shows Cameron independently created Avatar and did not use Morawski's ideas."

A relieved Cameron told TheWrap.com: "It is a sad reality of our business that whenever there is a successful film, people come out of the woodwork claiming that their ideas were used.

"Avatar was my most personal film, drawing upon themes and concepts that I had been exploring for decades. I am grateful that the court saw through the blatant falsity of Mr Morawski's claim."

WENN