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.