Bill Cipher is the main antagonist of the Disney Channel/Disney XD animated series Gravity Falls, serving as the overarching antagonist of Season 1 and the main antagonist of Season 2.

An immensely powerful dream demon from the Second Dimension who rules over the Nightmare Realm, Bill wants to bring chaos and destruction across the rest of known existence by achieving a physical form and opening a rift between the Nightmare Realm and Earth. He is also the arch-nemesis of the Pines family.