"Phineas and Ferb Christmas Vacation" is a special Christmas-themed episode of the animated television series Phineas and Ferb. The episode was originally broadcast on Disney XD on December 6, 2009. The special's narrative, set prior to the events of the series, follows protagonists Phineas and Ferb decorating their city for the arrival of Santa Claus. But when the evil mad scientist Dr. Heinz Doofenshmirtz uses a machine to ruin the holiday, Phineas and Ferb must find a way to fix it and save Christmas. The episode serves as the 37th broadcast episode of the second season, as well as the 84th broadcast episode overall.

"Phineas and Ferb Christmas Vacation" was written by Jon Colton Barry and Scott Peterson and directed by Zac Moncrief, who had been nominated for a 2009 Emmy award for his work on the episode "The Monster of Phineas-n-Ferbenstein" a few months before the special aired. It serves as a realization of a dream series co-creators Jeff "Swampy" Marsh and Dan Povenmire to have their own Christmas special, something they desired since their creation of the series. The special featured multiple guest stars including Clancy Brown, Malcolm McDowell, Jane Carr, Mathew Horne, and Bruce Mackinnon, and detailed seven original songs, including one performed by swing band Big Bad Voodoo Daddy.

"Phineas and Ferb's Christmas Vacation" received a large and widespread release from The Walt Disney Company, who showed optimism on it and promoted it through interviews and special broadcasts. When the episode premiered on Disney XD, it received 2.62 million viewers, ranking as the number 3 telecast in the night across all demographics. When the episode premiered on Disney Channel on December 11, 2009, it ranked as the number five program of the week with 5.213 million viewers. Critical reception from television critics and various media outlets was generally positive. It is also the first episode not to be set during the summer.