Robert Downey Jr. Rumored as Doom in Doomsday

Avengers: Doomsday is being positioned as Marvel Studios’ most ambitious crossover, bringing the Avengers, the Fantastic Four and numerous X‑Men‑era characters together to face Doctor Doom, who is reportedly being played by Robert Downey Jr. Insider rumors and leaked concept art/set photos suggest Doom may seize control of X‑universe Sentinels, though those plot details remain unconfirmed. Several original X‑Men actors are reported to be returning — including Patrick Stewart, Ian McKellen, Kelsey Grammer, Alan Cumming, James Marsden and Rebecca Romijn — while others such as Famke Janssen and Halle Berry have not been confirmed; Janssen says she is not part of the film as far as she knows. The Russo brothers are directing, principal photography reportedly wrapped on September 19, 2025, and the film is scheduled for release on December 18, 2026. Because reporting mixes official announcements, on‑set leaks and industry rumors (and some sources note unverified credits on databases like IMDb), readers should treat casting and plot specifics as unconfirmed until Marvel confirms them.