The singer/songwriter has revealed he was approached by Russell Crowe to write the script for the follow-up to the film, which won the actor an Oscar.
Movie experts thought the story was little more than a prank made up to entertain journalists at junkets and press conferences, but Cave has now admitted it's true.
He tells U.S. comedian Mark Maron's Wtf podcast, "He (Crowe) rang me up and asked if I wanted to write Gladiator 2. For someone who had only written one film script, it was quite an ask.
"(I said), 'Hey Russell, didn't you die in Gladiator 1?' 'Yeah, you sort that out.' So, he goes down to purgatory and is sent down by the gods, who are dying in heaven because there's this one god, there's this Christ character, down on Earth who is gaining popularity and so the many gods are dying so they send Gladiator back to kill Christ and his followers."
Cave adds, "I wanted to call it Christ Killer and in the end you find out that the main guy was his son, so he has to kill his son and he was tricked by the gods. He becomes this eternal warrior and it ends with this 20 minute war scene which follows all the wars in history, right up to Vietnam and all that sort of stuff and it was wild.
"It was a stone cold masterpiece. I enjoyed writing it very much because I knew on every level that it was never going to get made. Let's call it a popcorn dropper."