Patrick Sheane Duncan (born 1947) is an American writer, film producer and director.

A graduate of Grand Valley State University in Allendale, Michigan, Duncan's career has been influenced by his Vietnam War experiences, which inspired the television mini-series Vietnam War Story (1987) and its sequel Vietnam War Story: The Last Days (1989) and the films 84C MoPic (1989) and Courage Under Fire (1996). Additional writing credits include A Home of Our Own (1993), The Pornographer (1994), Nick of Time (1995), Mr. Holland's Opus (1995), and the television movies A Painted House (2003) and Elvis (2005).

Duncan is a winner of the CableACE Award for Writing for a Dramatic Series for Vietnam War Story: The Last Days and a Christopher Award for Mr. Holland's Opus, which also garnered him a Golden Globe nomination. He was nominated for the Grand Jury Prize at the Sundance Film Festival for 84C MoPic and The Pornographer and the Independent Spirit Award for Best First Feature and Best Screenplay for 84C MoPic.

Duncan's play, Souls on Fire was produced by Danny Glover's theatre company, Robey Theatre Company in Los Angeles.

Attended Grand Valley State University in Allendale, Michigan.

Was member of the dramatic jury at the Sundance Film Festival in 1997.