William Thomas Hader Jr. is an American actor, comedian, and filmmaker. With a filmography of varying genres, Hader has received various accolades, including three Primetime Emmy Awards, and nominations for two Golden Globe Awards, two Critics' Choice Television Awards, and four Screen Actors Guild Awards; among other guild awards and nominations for his efforts as a writer, director, producer. He is the creator, producer, writer, director, and star of the HBO dark comedy series Barry, for which he has been nominated for eight Primetime Emmy Awards, winning two. Hader's initial success was for his eight-year stint as a cast member on the long-running NBC variety series Saturday Night Live, for which he received four Primetime Emmy Award nominations and a Peabody Award.

A member of the Saturday Night Live cast, he is most recognized for his work as an actor, comedian, and writer. He has appeared in Superbad, Tropic Thunder, Trainwreck, and Forgetting Sarah Marshall, among other films. He produced and starred in the HBO series Barry in 2018.