Yes, that is Robert Downey Jr. as Doctor Doom in Fantastic Four, Marvel director confirms
That cameo is indeed Robert Downey Jr.

Yes, that mysterious cloaked figure in Fantastic Four is indeed played by Robert Downey Jr. – as confirmed by the director himself.
In the first of The Fantastic Four: First Steps post-credits scenes, Sue Storm stumbles upon Doctor Doom in the Baxter Building, taking an interest in young Franklin. Just what the supervillain wants isn't clear yet, but it most likely has something to do with the Power Cosmic residing within the kiddo.
But, since you don't see his face in the Russo brothers-directed scene, it wasn't entirely clear if that was indeed Robert Downey Jr.'s version of the character.
Well, the Phase Hero podcast asked The Fantastic Four: First Steps director Matt Shakman if Downey Jr. was the one in the suit, and Shakman replied very simply: "Yes, yes."
We'll likely find out more about Doom's plans in the aptly titled Avengers: Doomsday, which is coming out next December. However, it sounds like the script is still very much in flux. "[I'm] not quite sure [if Mystique's scenes have all been filmed]. They haven't finished writing it," Mystique actor Rebecca Romijn revealed at SDCC 2025. "They keep everything close to the vest themselves in an effort to keep everything under wraps."
That tracks with something Marvel boss Kevin Feige has shared about the movie, too. "There's plus-ing happening every day on the Avengers: Doomsday set right now, and it is amazing to watch because what those filmmakers, those actors, both the ones that are playing these characters for the first or second time and the one playing them for the 10th or 12th time, are the best in the world at it, and know these characters so well," Feige commented.
As for Downey Jr., he has recently shared another look at his comic book reading material, and he might be teasing a Doom vs. Iron Man showdown… We'll just have to wait and see.
Fantastic Four is in theaters now. For even more on the Marvel Phase 6 movie, check out our The Fantastic Four: First Steps review.

I'm the Deputy Entertainment Editor here at GamesRadar+, covering all things film and TV for the site's Total Film and SFX sections. I previously worked on the Disney magazines team at Immediate Media, and also wrote on the CBeebies, MEGA!, and Star Wars Galaxy titles after graduating with a BA in English.
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