The 44-year-old actor - who stars as a being from outer space in upcoming movie The Day the Earth Stood Still - has no doubt that there are other life forms in the universe.
Asked if he thinks there are "advanced extra-terrestrial life forms in the cosmos", Keanu replied: "I think it more likely than not. The cosmos is a pretty big place."
Keanu - who stars alongside Jennifer Connelly in the remake of the famous 1951 film - also spoke about the likelihood of returning to his role as Neo in another movie in The Matrix film franchise.
Recalling how Neo died in the last sci-fi film The Matrix Revolutions, when he unplugged himself to save both the humans and the Machines in the alternative world, Keanu told US TV show 'Extra': "Never say no but I don't think it's going to happen, and besides, I'm dead."