The fourth season of Family Guy aired on Fox from May 1, 2005, to May 21, 2006, and consists of thirty episodes, making it the longest season to date. The first half of the season is included within the volume 3 DVD box set, which released on November 29, 2005, and the second half within the volume 4 DVD box set, which released on November 14, 2006. Volume 4 is split into seasons 4 and 5 in regions outside the United States, leading to confusion over season numbers between U.S., Australian, and UK consumers. The last three episodes of season 4 are the basis for the movie known as Stewie Griffin: The Untold Story, and are edited for content; Fox does not include these episodes in the official episode count.

Family Guy is an American animated sitcom created by Seth MacFarlane for the Fox Broadcasting Company. The series premiered on January 31, 1999, following Super Bowl XXXIII, with the rest of the first season airing from April 11, 1999. The show centers around the Griffins, a dysfunctional family consisting of parents Peter and Lois, their children, Meg, Chris, and Stewie, and their anthropomorphic pet dog, Brian. Set in the fictional city of Quahog, Rhode Island, the show exhibits much of its humor in the form of metafictional cutaway gags that often lampoon American culture.