Allison Howell Williams (born April 13, 1988) is an American actress. She first received attention on YouTube and as a member of the improv comedy troupe Just Add Water. She then played Marnie Michaels in the HBO comedy-drama series Girls (2012–2017), receiving a Critics' Choice Award nomination. Her continued television roles include the Netflix black comedy A Series of Unfortunate Events (2018–2019) and the Showtime miniseries Fellow Travelers (2023).
Williams' film breakthrough came with Jordan Peele's psychological horror Get Out (2017), earning nominations at the MTV Movie Awards and the Screen Actors Guild Awards. She then starred in and produced the comedy horror films M3GAN (2022) and M3GAN 2.0 (2025). For her work in the horror genre, Williams has been deemed a scream queen.