Pi (stylized as π) is a 1998 American conceptual psychological thriller film written and directed by Darren Aronofsky (in his feature directorial debut). Pi was filmed on high-contrast black-and-white reversal film. The title refers to the mathematical constant pi. The story focuses on a mathematician with an obsession to find underlying complete order in the real world and contrasting two seemingly irreconcilable entities: the imperfect irrationality of humanity and the rigor and regularity of mathematics, specifically number theory. The film explores themes of religion, mysticism, and the relationship of the universe to mathematics.

The film received positive reviews and earned Aronofsky the Directing Award at the 1998 Sundance Film Festival, the Independent Spirit Award for Best First Screenplay and the Gotham Open Palm Award.