TMDb/Avengers: Doomsday Movie Marvel reveals Robert Downey Jr. returns to the MCU as Doctor Doom in Avengers: Doomsday, hitting theaters December 18, 2026. April 29, 2026 AceShowbiz - Avengers: Doomsday is set to hit theaters on December 18, 2026, and anticipation is building for the return of Robert Downey Jr. to the Marvel Cinematic Universe, not as the beloved Tony Stark/Iron Man, but in a surprising new role as the villainous Doctor Victor von Doom.