"It's a Sin to Tell a Lie" is a popular song written by Billy Mayhew and published in 1936. It became a major hit for The Ink Spots in 1941, whose recording featuring Bill Kenny's high tenor and Hoppy Jones's spoken bass interlude became one of their most recognizable performances. The song has since become a standard recorded by numerous artists across various genres, including Fats Waller, Willie Nelson, and many others.