Alexander Harper "Xander" Berkeley (born December 16, 1955) is an American actor. He is best known for his television roles as George Mason on 24, Sheriff Thomas McAllister on The Mentalist, Percy Rose on Nikita, the Man on The Booth at the End and Gregory on The Walking Dead. His film roles include Todd Voight in Terminator 2: Judgment Day, Trevor Lyle in Candyman, Ralph in Heat, Agent Gibbs in Air Force One and Dr. Lamar in Gattaca.
For Nickelodeon, he voiced Snav, Urbab, Abraham Lincoln, and Timmy in Aaahh!!! Real Monsters, a stoat and a barking deer on The Wild Thornberrys, and MacKenzie's father in the Rocket Power episode "Lost and Find".