IF is a 2024 American fantasy comedy film written and directed by John Krasinski, who also produced it alongside Allyson Seeger, Andrew Form, and Ryan Reynolds. The film features an ensemble cast including Cailey Fleming, Reynolds, Krasinski, and Fiona Shaw, with Alan Kim and Liza Colón-Zayas in supporting roles, alongside the voice talents of Phoebe Waller-Bridge, Louis Gossett Jr., and Steve Carell. Combining live-action and animation, the film follows a young girl (Fleming) who goes through a difficult experience and begins to see everyone's imaginary friends who have been left behind as their creators have grown up.

Development of the film began in 2019, with Krasinski set to write and direct and Reynolds attached to star. The rest of the cast joined between October 2021 and January 2022, and filming took place in New York City between August of that year and May 2023. IF was theatrically released by Paramount Pictures in the United States on May 17, 2024. The film received mixed reviews from critics and grossed over $190.3 million against a budget of $110 million.