"Little Willy" is a song written by songwriters Nicky Chinn and Mike Chapman and performed by the British glam rock band The Sweet, released in 1972 as a non-album single in the UK, peaking at number 4 in the UK Singles Chart.

It was released in the US in January 1973 and also appeared on their US debut album The Sweet and became their biggest hit in the US, reaching number 3 on the Billboard Hot 100.

In a retrospective review of glitter rock, Bomp!

noted that although rock music journalists almost uniformly "loathed it", the song was a huge commercial success and "helped launch the essential glitter rock formula sound".

[10] "Little Willy" was used extensively in the pilot of the television series Life on Mars.