Thomas Hagen is a fictional character in Mario Puzo's 1969 novel The Godfather and Francis Ford Coppola's films The Godfather (1972) and The Godfather Part II (1974). He is portrayed by Robert Duvall in the films. He also appears in the Mark Winegardner sequel novels The Godfather Returns and The Godfather's Revenge, as well as Ed Falco's novel The Family Corleone. Duvall was nominated for an Academy Award for Best Supporting Actor and a BAFTA for his performance in the first film.

Robert Selden Duvall is an American actor and filmmaker. With a career spanning seven decades, he is the recipient of an Academy Award, four Golden Globe Awards, a BAFTA Award, two Primetime Emmy Awards, and a Screen Actors Guild Award.