Raymond "Red" Reddington
Elizabeth "Liz" Keen
Donald Ressler
Harold Cooper
Tom Keen
Dembe Zuma
Aram Mojtabai
Samar Navabi

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 was most recently seen in the blockbuster sci-fi flick "Pacific Rim," directed by Guillermo del Toro, and he starred 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).

Prior to his role in "Homeland," Klattenhoff's big break came when he was cast to play Shane Oman in the cult classic movie "Mean Girls," where he collaborated with Tina Fey, Amy Poehler, Rachel McAdams, Amanda Seyfried and Lindsay Lohan. Since then, Klattenhoff has consistently worked on several films, including "The Dry Land," "Lucky Number Slevin" and "The Informers."

On the small screen, in addition to "Homeland," Klattenhoff has had memorable guest and recurring character appearances in series such as "Men in Trees," "ER," "Mercy," "Smallville," "Supernatural" and "Falling Skies."

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.