Factor Three is a short-lived supervillain subversive organization appearing in American comic books published by Marvel Comics. The group is usually depicted within the pages of The X-Men. It was led by the Mutant Master, who was secretly an alien from a race of beings from Sirius that resemble octopuses. It used various mind control methods to capture and train new agents, though some merely joined for profit. The Factor Three saga, as the storyline has become unofficially known in the years since, was one of the earliest multipart storylines in the team's history.