Scott Kosar is an American screenwriter whose films include The Machinist, the 2003 remake of the classic horror film The Texas Chain Saw Massacre, and the 2005 remake of The Amityville Horror. In June 2006, he was presented with the Distinguished Achievement in Screenwriting Award by the UCLA School of Theater, Film and Television. Kosar was appointed the Hunter/Zakin screenwriting chair at UCLA for 2009–2010.

The Machinist is a 2004 psychological thriller film directed by Brad Anderson and written by Scott Kosar. It stars Christian Bale as the title character, a machinist struggling with paranoia and delusion after being unable to sleep for an entire year. Jennifer Jason Leigh, Aitana Sánchez-Gijón, John Sharian, and Michael Ironside appear in supporting roles.