Joanna Merlin (born Joann Ratner; July 15, 1931) was an American actress and casting director who has worked with Stephen Sondheim and starred in the original Broadway production of Fiddler on the Roof. She has written two acting guides and is a faculty member of New York University's graduate acting program. In recent years, she has become known for her recurring role on Law & Order: Special Victims Unit as Judge Lena Petrovsky.