Mary Lynn Rajskub (born June 22, 1971) is an American actress and comedian, best known for her roles as Chloe O'Brian on the Fox action-thriller 24, Norah in The Tomorrow War, Theresa in Night School, Erin Roberts on the Starz series The Girlfriend Experience, Captain Davis in The Kings of Summer, Bridget Bay in Safety Not Guaranteed, Sarah in Julie & Julia, Lynn in Sunshine Cleaning, Janet Stone in Firewall, Reena Giuliani in Legally Blonde 2, Elizabeth Egan in Punch-Drunk Love, Dorothea in Sweet Home Alabama, and Zelmina in Dude, Where's My Car?.

She has also had recurring roles as Lorraine Fuisz on the Hulu series The Dropout, Genevieve Mirren-Carter on Brooklyn Nine-Nine, Goldie on Californication, and Gail the Snail on the FX series It's Always Sunny in Philadelphia.