Gregory Stephen Poirier (born 19 May 1961) is an American film and television writer and director, and producer.

Poirier was born in Kula, Maui, Hawaii. He attended the Maui Academy of Performing Arts. He graduated from the University of Southern California with a BFA in theater and UCLA with an MFA in screenwriting. Poirier wrote the screenplay for the John Singleton film Rosewood (1997), for which he won the Writers Guild of America's Paul Selvin Award. He wrote the screenplay for the comedy See Spot Run, and wrote and directed the comedy Tomcats (2001). And also a draft of Superman Returns.

He also wrote The Lion King II: Simba's Pride, A Sound Of Thunder, Gossip, and National Treasure: Book of Secrets., and the Jackie Chan film "The Spy Next Door".

Poirier is creator, executive producer and writer of the upcoming ABC mystery series Missing, starring Ashley Judd, which is scheduled to debut March 15, 2012.