Kathleen Erin Walsh (born October 13, 1967) is an American actress. She is best known for her role as Dr. Addison Montgomery on the ABC television dramas Grey's Anatomy and Private Practice.

She is also known for her roles as Rebecca Wright on the short-lived NBC sitcom Bad Judge

Walsh was born in San Jose, California, the daughter of Angela and Joseph Patrick Walsh Sr.

She grew up in a Catholic household in Tucson, Arizona.

Her mother is of Italian descent,[and her father was Irish, from Navan in County Meath.

Walsh graduated from Catalina Magnet High School and studied acting at the University of Arizona before dropping out.

Walsh moved to New York City and joined a comedy troupe, Burn Manhattan, supporting herself by waitressing.

She performed on National Public Radio in the production of the radio play Born Guilty.

In 2014, Walsh had a supporting role in the first season of FX's television series Fargo.