Robert Downey Jr. to Return to the MCU as Doctor Doom in 'Avengers: Doomsday'

He's baaaack!

Robert Downey Jr. is returning to the MCU, and this time, there's no question about whether or not he's the bad guy.

The Marvel legend made an epic surprise return during the studio's Hall H panel at San Diego Comic-Con on Saturday, taking the stage following the reveal of Joe and Anthony Russo's return to direct the next two Avengers films.

As it turns out, Avengers 5 -- which was previously titled Avengers: The Kang Dynasty, but scrapped amid Jonathan Majors' ongoing legal issues -- is now titled Avengers: Doomsday, with Downey as its villainous mastermind.

The Russos said that cast Downey -- who, obviously, played MCU mainstay Tony Stark, aka Iron Man, in nine MCU films -- "proof of the unimaginable possibilites in the Marvel multi-universe."

"I mean, this is potentially one of the more entertaining characters in all of fiction," they teased before Downey's big reveal. "If we're gonna do this, if we're gonna bring him to movie theaters worldwide, then I think were gonna need the greatest actor in the world to play that character."

"New mask, same task. What'd I tell you, I like playing complicated characters," Downey told the Comic-Con crowd.

Avengers: Doomsday will kick off the end of the MCU's Phase 6 in May 2026, followed by Avengers: Secret Wars in May 2027.

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