Graham John Yost (born September 5, 1959) is a Canadian film and television screenwriter. His best-known works are the films Speed, Broken Arrow, and Hard Rain and the TV series Justified. In 2002, he created the widely acclaimed, yet short-lived drama series Boomtown.

He has also written for the television series Herman's Head and Band of Brothers. He also created the short-lived NBC drama Raines. Yost teamed up with Tom Hanks and Steven Spielberg, along with two of his fellow Boomtown writers Michelle Ashford and Larry Andries, to write and direct episodes of the HBO miniseries The Pacific. As of 2010, Yost is the creator and executive producer of the series Justified, which premiered on FX in March 2010.

Born in Etobicoke, he is the son of Canadian television personality Elwy Yost, the longtime host of the public broadcaster TVOntario's Saturday Night at the Movies. He lives in California with his family.