Avatar director and writer James Cameron has promised fans four sequels, instead of the previously-planned three.
Fox plans to release the first of the sequels at the end of 2018, with the others in 2020, 2022 and 2023, according to The Hollywood Reporter.
Cameron made the announcement when he appeared as a surprise guest at Fox's CinemaCon in Las Vegas on Thursday.
The filmmaker said he had found the idea of three sequels to be limiting.
"We began to bump up against the limitations for our art form," he said, explaining that he needed more instalments to tell the whole story.
"I've been working the last couple of years with a team of four top screenwriters," he said, "to design the world of Avatar going forward: the characters, the creatures, the environment, the new cultures.
"So far, the art I'm seeing is, in pure imagination, really far beyond the first film," he added. "It's going to be a true epic saga."
He will also be hoping that the films' box office takings can be equally as epic - the original in 2009 earned $2.8bn (£1.98bn) worldwide.