The Venice film festival has opened with a brilliant superhero dark comedy that delves into the cinema and theatre worlds to explore the drug that is fame.

The first flick to compete at the world's oldest film festival, Mexican director Alejandro Gonzalez Inarritu's Birdman, or the Unexpected Virtue of Ignorance, stars Michael Keaton of Beetlejuice and Batman fame.

In one of 20 films vying for the coveted Golden Lion award, Keaton plays a washed-up actor who was once famous for playing the Birdman superhero but is now struggling to stage a Broadway play in a bid to regain his former glory.

For all his attempts to create a worthy on-stage performance, he finds it increasingly difficult to leave the Birdman character behind.

Keaton said he was not haunted by his Batman films - but that everyone is by their own personal Birdman.

"You all got a Birdman in your life, it's your negative ego."

Gonzalez Inarritu, best known for 21 Grams and Babel, brought on board other superhero veterans for the movie, including Emma Stone from The Amazing Spider-Man and Edward Norton of The Incredible Hulk.

- AAP