Greg Marcks (born August 12, 1976) is an American director and screenwriter of motion pictures.

Marcks wrote and directed the highly acclaimed indie film 11:14 starring Hilary Swank, Patrick Swayze, Barbara Hershey, Rachael Leigh Cook, Ben Foster, and Colin Hanks.

His film Echelon Conspiracy, an action thriller film starring Shane West, Edward Burns, Martin Sheen, Jonathan Pryce and Ving Rhames was released theatrically in the U.S. on February 27, 2009.

The film, though fiction, deals with the real-world SIGINT collection program ECHELON, run by the NSA.

Marcks' next project, a film based on You Don't Love Me Yet, a novel by Jonathan Lethem, deals with the romantic escapades of bandmates living in the Silver Lake neighborhood of Los Angeles, California.