Katherine Moennig (born December 29, 1976) is an American actress.

Born in Philadelphia, Pennsylvania, she is the daughter of Broadway dancer and violin maker William Moennig. She is also the niece of actress Blythe Danner and cousin of Oscar winner Gwyneth Paltrow, who she says is very different from herself.

Moennig moved to New York City at the age of 18 to study at the American Academy of Dramatic Arts. There she began a modeling career, and also performed on stage.

In 1999, she had the central role of the Our Lady Peace video, "Is Anybody Home?"

Her first major role was in television series Young Americans, playing Jacqueline "Jake" Pratt, a girl that enters the Rawley Boys Academy by passing as a boy and ends up falling in love with Hamilton (Ian Somerhalder), the Dean's son. Her androgynous look helped her a lot for this role. She also auditioned for the part of Brandon Teena in Boys Don't Cry - that part ended up going to actress Hillary Swank. She did play the part of pre-op MTF Cheryl Avery in Law & Order: SVU (episode "Fallacy").

Since 2004, Moennig plays one of the main characters in The L Word. Her character is Shane McCutcheon, a hairdresser and heartbreaker who goes from one girl to another, but ends struggling with her lifestyle after meeting Carmen de la Pica Morales (Sarah Shahi).

On April 12, 2006, Moennig made her Off-Broadway debut in Guardians, a play by Peter Morris. In it, she plays "American Girl" - a young United States Army soldier from West Virginia who becomes a scapegoat in a scandal involving abuse at an Iraqi prison. The story is loosely based on that of Lynndie England.