Sweet Polly Oliver is an English folk song (Roud #367), dating from at least 1840. It is also known as "Pretty Polly Oliver". It is one of the best known of a number of folk songs describing woman disguising themselves as men to join the army. The song is mentioned in Terry Pratchett's Monstrous Regiment, as the song Polly Perks remembered from her childhood, which inspires her to choose "Oliver" as her military name. Thomas Root wrote a symphonic band arrnagement of Sweet Polly Oliver.