Justin W. Chambers (born July 11, 1970) is an American actor and former Calvin Klein male fashion model. As of 2005, he is starring in the ABC drama series Grey's Anatomy as Dr. Alex Karev.

Justin Chambers, a former male fashion model who was discovered by a modeling scout in a Paris Metro station and went on a campaign to represent Calvin Klein's fragrance, is now starring as Dr. Alex Karev on ABC's "Grey's Anatomy" (2005). He was born on July 11, 1970, in Springfield, Ohio, USA. His is one of five children of John Chambers and Pam Chambers, an Irish-German-American family. He has a twin brother named Jason, one older brother and two older sisters. While on vacation in Paris he was spotted by an agent in a Paris Metro station and soon went on modeling for Calvin Klein, Giorgio Armani, and others throughout Europe, Japan and United States. In the 1990s he settled in New York, where he studied at H.B. Studios for 4 years. That schooling yielded him appearances in several off-Broadway stage productions and a few television roles. Chambers' first break came in 1995, a four-month gig on a long-running NBC's daytime soap 'Another World', then he appeared opposite Lolita Davidovich in 'Harvest of Shame' (1996) and in CBS's 'Rose Hill' (1997) opposite 'Jennifer Garner'. After that he catapulted to the "IT" list of the late 1990s and was described as "part James Dean, part Marlon Brando" by Harper's Bazaar in 1998. He made his big screen debut in the featured role of a rich WASP who befriended a Jewish kid in Liberty Heights (1999), a Barry Levinson (I) drama. He then starred as D'Artagnan in Musketeer, The (2001) alongside Catherine Deneuve and Mena Suvari, then co-starred with Matthew McConaughey and Jennifer Lopez (I) in Wedding Planner, The (2001). His career slowed down for a few years, yielding little meaningful exposure in films and on TV, with the exception of a supporting role alongside Uma Thurman and Gena Rowlands in HBO's _Hysterical Blindness (2002 TV movie)_. In 2005 Chambers made a comeback starring as Dr. Alex Karev opposite Katherine Heigl on ABC's Grey's Anatomy. He also starred as obsessed police detective, Sgt. Matt Parish, in the thriller Zodiac, The (2005). Justin Chambers has been enjoying a happy family life. He is a father of five children with his wife, Keisha Chambers, a model agency booker, whom he met while he was modeling with Calvin Klein. The two have been married since 1993. A longtime New Yorker, he used to travel back and forth from New York to L.A. while his family was still in New York. His wife and children have recently moved to LA with Justin from their New York home.