Fox William Mulder is a fictional FBI Special Agent and the secondary protagonist of the Fox science fiction-supernatural television series The X-Files, played by David Duchovny. Mulder's peers dismiss his many theories on extraterrestrial or paranormal activity as those of a conspiracy theorist and supernaturalist; however, his skeptical but supportive partner, Special Agent Dana Scully, often finds them to be unexpectedly correct. He and Scully work in the X-Files office, concerned with unsolved FBI cases that are often revealed to be supernatural or extraterrestrial in nature. Mulder was a main character for the first seven seasons, but was limited to a recurring character for the following two seasons. He returns as a main character for the tenth and eleventh seasons.

The seventh season of the American science fiction television series The X-Files commenced airing on the Fox network in the United States on November 7, 1999, concluded on May 21, 2000, and consists of twenty-two episodes. Taking place after the destruction of the Syndicate, this season marks the end of various other story lines; during this season, Fox Mulder learned the true fate of his sister, Samantha.