The X-Mansion or Xavier Institute is the common name for a mansion and research institute appearing in American comic books published by Marvel Comics. The mansion is depicted as the private estate of Charles Francis Xavier, a character in X-Men comics. It serves as the base of operations and training site of the X-Men. It is also the location of an accredited private school for mutant children, teenagers, and sometimes older aged mutants, the Xavier Institute for Higher Learning, formerly the Xavier School for Gifted Youngsters. The X-Mansion is also the worldwide headquarters of the X-Corporation.

The X-Mansion's address is 1407 Graymalkin Lane, Salem Center, located in Westchester County, New York. The school's motto is "mutatis mutandis". In a recent edition of the comic, Wolverine re-opened the school, at the same address, under the name of the Jean Grey School for Higher Learning. After it was discovered that the Terrigen Cloud had become toxic to mutants enough to have them die from M-Pox, Storm had the mansion moved to Limbo and renamed it X-Haven to keep mutants safe from the Terrigen until a cure could be discovered. After Medusa destroys the Terrigen Cloud so the mutants could survive, Kitty Pryde moves the mansion from Limbo to Central Park, New York, and renames it the Xavier Institute for Mutant Education and Outreach.