Blair Underwood (born August 25, 1964) is an American television and film actor. He is best known for his role as the headstrong attorney Jonathan Rollins in the NBC legal drama L.A. Law, which he played for seven years. Over the course of his career, he has received critical acclaim, numerous Golden Globe nominations, three NAACP Image Awards, and one Grammy Award.

His feature film debut came in the 1985 film Krush Groove. An appearance in 1985 on The Cosby Show led to a short role on the ABC soap opera One Life to Live, which ultimately led to his role on the television series L.A. Law, where he appeared from 1987 to 1994.

Underwood broke into film with roles in Just Cause (1995), Set It Off (1996), and Deep Impact (1998). He also had a supporting role as a geneticist in Gattaca. In 2000, he starred in the short-lived television series City of Angels. In 2003, he appeared in four episodes of the HBO series Sex and the City, playing the love interest of Cynthia Nixon's character. In 2004, he played the role of Roger De Souza alongside Heather Locklear in the NBC series LAX.

He received acclaim for his role as a sexy elementary school teacher in the CBS sitcom The New Adventures of Old Christine alongside Julia Louis-Dreyfus for two years. In 2007, he appeared in an episode of the NBC series Law & Order: Special Victims Unit. He also had the recurring role of Alex in the HBO series In Treatment. Also in 2007, Underwood co-wrote the novel Casanegra: A Tennyson Hardwick Novel with the married couple Steven Barnes and Tananarive Due.