The cult comedy troupe of John Cleese, Michael Palin, Eric Idle, Terry Gilliam and Terry Jones are kicking off their reunion gigs tomorrow.
Hawking will appear in the show, at London's O2, with Professor Brian Cox and a cast including a full orchestra and dozens of dancers.
Idle said: "He's a big Python fan so he was asked if he would and he said within one minute 'yes'."
Cleese said the show, which includes numerous set changes and special effects, costs around £4.5 million to stage.
He said: "It's much more complicated and spectacular than certainly I realised when we sat down for the read-through for the first time."