Raymond "Red" Reddington
Elizabeth "Liz" Keen
Donald Ressler
Harold Cooper
Ryan Eggold
Tom Keen

Diego Klattenhoff

Donald Ressler

Diego Klattenhoff stars as FBI agent Donald Ressler on NBC's high-action government crime thriller "The Blacklist."

With distinguished roles in a variety of projects, Klattenhoff currently appears as a series regular on the Golden Globe-winning and Emmy-nominated series "Homeland" as Major Mike Faber, best friend to Nicholas Brody (Damian Lewis).

Klattenhoff's big break came when he was cast to play Shane Oman in the cult classic movie "Mean Girls," where he had a chance to work with Tina Fey, Amy Poehler, Rachel McAdams, Amanda Seyfried and Lindsay Lohan. Since then, Klattenhoff has consistently worked on major films, including "The Dry Land," "Lucky Number Slevin" and "The Informers." Klattenhoff can be seen in the highly anticipated sci-fi thriller "Pacific Rim," directed by Guillermo del Toro. The film is set in a world where soldiers piloting giant robots battle against monsters that have mysteriously risen from five miles beneath the ocean.

On the small screen, in addition to "Homeland," Klattenhoff has had memorable guest and recurring character appearances in series like "Men in Trees" with Anne Heche, "ER," "Mercy" and "Falling Skies." He has had the opportunity to work with Tom Welling in "Smallville" and Jensen Ackles and Jared Padalecki in "Supernatural." Additionally, he had the opportunity to meet Michael Klick, producer of "Homeland," while working on the set of "24" alongside Jon Voight.

Donald Ressler is a veteran FBI field agent who has been assigned to track Raymond Reddington for the bulk of his career. He was shocked when Reddington turned himself in - and frustrated when, despite his experience and expertise, Red refused to work with him directly. Initially antagonistic, even hostile, the relationship between Red and Ressler has become less strained over the last year - particularly after Red worked tirelessly to save Ressler's life during Anslo Garrick's siege of the Post Office, and later when Red helped bring the men who murdered his fiancée to justice.