Jigsaw is a fictional serial killer within the Saw universe. He is different from most fictional serial killers as he does not kill his victims directly, but instead relies on various lethal traps in which he places his victims.
Jigsaw believes that he has never killed anyone in his life and that the choices that his victims make are up to them. He believes this because he has cancer and failed to commit suicide and realized how life is a gift.
In the saw movies, jigsaw is the killer.