Zak Penn is an American screenwriter. Penn wrote and directed Incident at Loch Ness and The Grand, wrote the script for The Incredible Hulk, co-wrote the scripts for X2, X-Men: The Last Stand, and the story for The Avengers. With Michael Karnow, Penn is the co-creator of the TV series Alphas on the Syfy network.

X-Men: The Last Stand is a 2006 superhero film based on the X-Men comic books published by Marvel Entertainment Group. It is the sequel to X2, as well as the third installment in the X-Men film series, and was directed by Brett Ratner. It features an ensemble cast including Hugh Jackman, Halle Berry, Ian McKellen, Famke Janssen, Anna Paquin, Kelsey Grammer, James Marsden, Rebecca Romijn, Shawn Ashmore, Aaron Stanford, Vinnie Jones, and Patrick Stewart. Written by Simon Kinberg and Zak Penn, the film is loosely based on two X-Men comic book story arcs, "Gifted" and "The Dark Phoenix Saga", with a plot that revolves around a "mutant cure" that causes serious repercussions among mutants and humans, and on the resurrection of Jean Grey who unleashes a dark force.