Justin Willman Chambers is an American actor and former model. He is best known for his role as Dr. Alex Karev in the ABC television medical drama Grey's Anatomy from 2005 to 2020. Born in Ohio, he went to Southeastern High School, South Charleston, and later studied acting at New York's HB Studio. Chambers began modeling after being approached by a modeling scout in Paris. He went on to represent fashion brands including Calvin Klein, Armani, and Dolce & Gabbana. Chambers began his acting career with a recurring role in the soap opera Another World and made his feature film debut with a supporting role in the comedy drama Liberty Heights (1999).

Alexander Michael Karev,, M.D., F.A.C.S. is a fictional character on the ABC television series Grey's Anatomy, portrayed by actor Justin Chambers. Introduced as a surgical intern at the fictional Seattle Grace Hospital, Karev eventually obtained the position of resident, later becoming a pediatric surgeon. He then becomes Interim Chief of surgery for a six-month period while Bailey is on a "stress sabbatical". The relationships among colleagues Meredith Grey, Cristina Yang, Izzie Stevens and George O'Malley formed a focal point of the series.