The sixteenth season of the American animated television series The Simpsons began airing on Sunday, November 7, 2004, and finished airing on Sunday, May 15, 2005. It contained 21 episodes, beginning with Treehouse of Horror XV. The season contains six hold-over episodes from the season 15 (FABF) production line. Season 16 was released on DVD and Blu-ray in Region 1 on December 3, 2013, Region 2 on December 2, 2013, and Region 4 on December 11, 2013.

"Treehouse of Horror XV" is the first episode of the sixteenth season of the American animated television series The Simpsons. It originally aired on the Fox network in the United States on November 7, 2004. In the fifteenth annual Treehouse of Horror, Ned Flanders' head injury gives him the power to predict others' deaths, Bart and Lisa play detective when a string of Victorian-era prostitutes are murdered by Jack the Ripper, and the Simpsons go on a fantastic voyage inside Mr. Burns' body to save Maggie. It was written by Bill Odenkirk and directed by David Silverman. Around 11.29 million Americans tuned in to watch the episode during its original broadcast. Airing on November 7, it is the latest date that a Treehouse of Horror has aired, but had to be held back a week due to Fox's contractual obligation to air the World Series.