Sylvester Stallone is set to star in upcoming superhero movie Samaritan.

The 73-year-old has confirmed his next project, which will follow the story of a young boy who is on a mission to find out if a mythical superhero is still alive after vanishing 20 years earlier following a "tragic event".

Executives at MGM Studios have signed up Julius Avery to direct the project, and the Overlord filmmaker raved about his casting coup in a statement to Deadline.

"Sly is a hero of mine (and) I'm incredibly thrilled to be working with such an iconic actor on this very special project," he said.

Stallone's role in the project has not yet been announced, but reports suggest he'll portray the missing superhero.

The film will be the first release for Balboa Productions, the company Stallone launched with business partner Braden Aftergood last year.

Bragi F. Schut, who has worked with Stallone on Escape Room and its sequel, will pen the script, and also serve as an executive producer, according to the outlet.

MGM is currently in development with Balboa Productions on a separate project about the boxer Jack Johnson, who became the first African-American heavyweight champion in 1908.

He was jailed in 1920 and posthumously pardoned by U.S. President Donald Trump in May last year, 105 years after his conviction.

News of Stallone's superhero movie comes just days after his latest instalment in the Rambo franchise, Last Blood, debuted in third place at the U.S. box office with a $19 million (£15.2 million) opening.