Cancer Man (sometimes referred to as the Smoking Man, the Cigarette-Smoking Man, CSM or C-Man) is a fictional character and the antagonist on the American science fiction television series The X-Files
. He serves as the arch-nemesis of FBI Special Agent Fox Mulder. Although his name is revealed to be C.G.B. Spender in the show's sixth season, fans continue to refer to him as the Cancer Man
because he is almost always seen chain-smoking Morley cigarettes and because he, like other series villains, has multiple aliases.
Although he utters only four audible words in the entire first season of the show, Cancer Man
eventually develops into the series' primary antagonist. In his early appearances, he is seen in the offices of Division Chief Scott Blevins and Assistant Director Walter Skinner, Mulder and his partner Dana Scully's supervisors. He works for a government conspiracy only known as the Syndicate, who are hiding the truth of alien existence and their plan to colonize Earth. Though it would seem he is a hard and fast enemy of Mulder and Scully, he seems to split time between being an enemy and, in part, an ally.