What If...? is an American animated anthology television series created by A. C. Bradley for the streaming service Disney+ based on the Marvel Comics series of the same name. It is the fourth television series in the Marvel Cinematic Universe (MCU) from Marvel Studios, the first animated series from the studio, and the first series produced by Marvel Studios Animation. The series explores alternate timelines in the multiverse that show what would happen if major moments from the MCU films occurred differently. Bradley served as head writer for the first two seasons, with Matthew Chauncey taking over for the third, and Bryan Andrews as the lead director.

Jeffrey Wright stars as the Watcher, who narrates the series, alongside many MCU film actors reprising their roles. Marvel Studios was developing the series for Disney+ by the end of 2018, with Bradley and Andrews on board. It was officially announced in April 2019. Marvel Studios' head of visual development Ryan Meinerding helped define the series' cel-shaded animation style, which was designed to reflect the films and take inspiration from classic American illustrators. Animation for the series was provided by Flying Bark Productions and Stellar Creative Lab, with Blue Spirit and Squeeze also working on the first season and SDFX Studios working on the second. Stephan Franck was head of animation for the first season and a director on the second and third seasons, with Scott Wright as head of animation for the second and third seasons. Chauncey was the series' story editor before replacing Bradley as head writer.

The first season of What If...? premiered on August 11, 2021, and ran for nine episodes until October 6, as part of Phase Four of the MCU. The second season was released daily from December 22 to 30, 2023, and the third and final season premiered on December 22, 2024, also releasing daily; both are part of Phase Five. The series has received generally positive reviews, with praise for the voice acting, animation, creative storylines, and scenarios, although the episodes' length and writing received some criticism. An interactive augmented and virtual reality story for the Apple Vision Pro headset, What If...? – An Immersive Story, was released in May 2024, and a spin-off series titled Marvel Zombies is set to premiere in October 2025.