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.

Incident at Loch Ness is a 2004 mockumentary starring, produced by and written by Werner Herzog and Zak Penn, while also serving as the latter's directorial debut. The small cast film follows Herzog and his crew while working on the production of a movie project on the Loch Ness Monster titled Enigma of Loch Ness. Incident at Loch Ness won the New American Cinema Award at the 2004 Seattle International Film Festival.