Kathleen Erin Walsh (born October 13, 1967) is an American actress and businesswoman. She is best known for her role as Dr. Addison Montgomery in the ABC medical drama series Grey's Anatomy (2005–2012, 2021–2023, 2026) and Private Practice (2007–2013). Walsh is also known for her roles as Nicki Fifer in the ABC sitcom The Drew Carey Show (1997–2002), Rebecca Wright in the NBC legal sitcom Bad Judge (2014–2015), Olivia Baker in the Netflix teen drama series 13 Reasons Why (2017–2019), The Handler in the Netflix superhero drama series The Umbrella Academy (2019–2024), and Madeline Wheeler in the Netflix comedy-drama series Emily in Paris (2020–present).