Diego Klattenhoff (born November 30, 1979) is a Canadian actor known for his portrayals of Mike Faber in the Showtime series Homeland and as FBI Agent Donald Ressler in The Blacklist. He has also appeared as Derek in Whistler and Ivan in Men in Trees.
Klattenhoff was born in French River, Nova Scotia. He moved to Toronto at the age of 19 to pursue an acting career. For a number of years, he worked as a bartender while studying in theater workshops.
Klattenhoff studied with some of Canada's most respected acting coaches, including David Rotenberg, Bruce Clayton and Rae Ellen Bodie. His first notable acting role was in Mean Girls (2004). He followed that with a string of appearances in notable TV shows like Smallville and Stargate SG-1, and films like Lucky Number Slevin (2006). Since 2006, he has been in recurring roles like Young Jacob in CBC Television's At the Hotel, Derek in CTV's Whistler, Ivan Palacinke in ABC's Men in Trees and Mike Callahan in NBC's Mercy.