FBI Assistant Director Walter Sergei Skinner is a fictional character in the Fox science fiction-supernatural television shows "The X-Files" and "The Lone Gunmen" portrayed by American actor Mitch Pileggi. Skinner supervised the X-Files office, which is concerned with cases with particularly mysterious or possibly supernatural circumstances that were left unsolved and shelved by the FBI. Fox Mulder, the FBI agent in charge of the X-Files, considers the X-Files the truth behind the supposed conspiracy. Skinner was a main character in the ninth, tenth and eleventh seasons of the show and a recurring character throughout the first eight seasons.