Billy Liar is a novel by Keith Waterhouse. It concerns the activities of a Walter Mitty-style character, a young man from a working-class background who has greater aspirations.

In 1963, it was made into a film with Tom Courtenay in the role of Billy and Julie Christie as his love interest. Mona Washbourne played his mother, and Wilfred Pickles his father. Rodney Bewes played his best friend.

The novel was also used as the basis for a television sitcom series of the 1970s (which has never been rerun), and was made into a successful West End musical (entitled simply Billy) starring Michael Crawford.

Waterhouse later wrote a sequel called Billy Liar on the Moon