Katherine Sian Moennig (born December 29, 1977) is an American actress best known for her role as Shane McCutcheon on The L Word, as well as Jake Pratt on Young Americans. In 2009, she starred as Dr. Miranda Foster on CBS Three Rivers. Moennig was born in Philadelphia, Pennsylvania, to Broadway dancer Mary Zahn and violin maker William H. Moennig III. Moennig is of German, Scottish, and Irish ancestry.

Moennig moved to New York City at the age of 18 to study at the American Academy of Dramatic Arts. Moennig has played multiple lesbian roles in The L Word, Everybody's Fine, Art School Confidential. She has also pursued transgender roles, auditioning for the part of Brandon Teena in Boys Don't Cry, and playing Cheryl Avery, a young transgender woman in Law and Order. In 2007, the documentary My Address: A Look At Gay Youth Homelessness in New York was launched with Moennig in cooperation with the Hetrick-Martin Institute (HMI).