Foster's Home for Imaginary Friends is an American animated television series created by Craig McCracken for Cartoon Network. It was produced by Cartoon Network Studios as the network's first show animated primarily with Adobe Flash, which was done both by Cartoon Network Studios in Burbank and in Ireland by Boulder Media. Set in a world in which imaginary friends coexist with humans, the series centers on Mac, an eight-year-old boy who is pressured by his mother to abandon his imaginary friend Bloo. After the duo discover an orphanage dedicated to housing abandoned imaginary friends, Bloo moves into the home and is kept from adoption as long as Mac visits him every day. The episodes revolve around Mac and Bloo as they interact with other imaginary friends and house staff and live out their day-to-day adventures, often getting caught up in various predicaments.

McCracken conceived the series with his partner Lauren Faust after they adopted two dogs from an animal shelter and applied the concept to imaginary friends. The series first premiered on Cartoon Network on August 13, 2004, as a 90-minute television film. On August 20, it began its normal run of 22-minute episodes on the Fridays block. The series finished its run on May 3, 2009, with a total of 6 seasons and 79 episodes. McCracken left Cartoon Network shortly after the series ended.

Foster's Home for Imaginary Friends received critical acclaim for its animation, humor, writing, characters, and music. It became one of Cartoon Network's most successful original series and received numerous industry accolades, including five Annie Awards and seven Emmy Awards, winning a total of 12 awards out of 35 nominations. It has since been named by Entertainment Weekly as one of the best Cartoon Network shows and by IGN in their list of best animated series at number 85.

A spinoff, Foster's Funtime for Imaginary Friends, announced as having begun development on July 18, 2022, and greenlit to series on June 12, 2024, produced by Hanna-Barbera Studios Europe with Craig McCracken returning as the creator. The spinoff, aimed at a preschool audience, features a new cast of young imaginary friends, along with Bloo and Madame Foster from the original series.