The actor will make his West End debut when he takes on the role of Patsy on 23 September (13).
Davis, who also appeared in the Star Wars movies and cult fantasy film Willow, reveals he jumped at the chance to play a part in the Monty Python production: "As a kid I was always a massive fan of Monty Python so when Spamalot came to town I thought, 'I'd really love to be in that'. And now I'm excited that I'm actually not just in it, but playing the lead role.
"I've been in hit Tv shows and blockbuster Hollywood movies, but you are never really taken seriously as an actor until you've done a play."
He'll join comedian and British Tv personality Les Dennis, who will take on the role of King Artur in the production.