"It's a Sin" is a song recorded by English synthpop duo the Pet Shop Boys (consisting of Neil Tennant and Chris Lowe) which reached number one on the UK Singles Chart for three weeks in 1987, and was their third top ten in the US when it reached number nine on the Billboard Hot 100.

The song is a description of Tennant's Catholic upbringing and education at St. Cuthbert's High School in Newcastle upon Tyne, implying that everything that is perceived to be pleasurable in life is regarded as sinful. The song uses extensive samples from Latin masses and religious imagery throughout to reinforce the feel of the song. Tennant has said that he wrote the lyrics in 15 minutes, purging his emotions in a moment of frustration and anger.

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