Leighton Marissa Claire Meester (born April 9, 1986) is an American actress, best known for her role as Blair Waldorf in the TV show Gossip Girl. Her first acting role on a television program was on NBC's legal drama Law & Order in 1999. Other series in which Meester has appeared include CSI: Miami, 8 Simple Rules, 24, 7th Heaven, and House.

Currently, Meester stars as Blair Waldorf in The CW series Gossip Girl, from Josh Schwartz, creator of The O.C. and based on the book series about the lives of New York's two privileged Upper East Side high school students. Meester has stated in interviews that she identifies with Blair "on every level, in one way or another." She has also recently guest starred on CSI: Miami and has a recurring role on James Woods' court drama Shark. When not on the set, Meester, who attended Beverly Hills High School, pursues her talent for music and creative writing. She currently resides in New York.

She has worked with actress Kristen Bell on two TV series. In Gossip Girl, Bell provides the voice of Gossip Girl and Leighton plays Blair Waldorf, and in Veronica Mars, which stars Bell, Leighton appeared briefly as gossip queen Carrie Bishop.

She will reprise her role of Justine Chapin on Entourage in season five.

Although yet to be confirmed Leighton who recorded a single for Drive-Thru might be releasing a debut album but is still unconfirmed and may just be rumors.