"20th Century Boy" is a song by T. Rex, written by Marc Bolan. It was released as a single in 1973 and reached #3 in the UK Singles Chart. The song did not feature on an original studio album but was included as a bonus track on a reissue of 1973 album Tanx.
It later returned to the UK Top 20 in 1991, peaking at #13, fourteen years after Bolan's death, when it was used in a Chris Hartwill-directed commercial for Levi's starring Brad Pitt. A slightly different segment of the song, with the addition of a harp, was used in a Jameson Irish Whiskey television advertisement. It plays a key role on the science fiction-mysterymanga20th Century Boys.
On 8 September 2011 a new musical called 20th Century Boy opened at the New Wolsey Theatre in Ipswich. The actor-musician production is a world premiere produced by the New Wolsey Theatre, Bolanic Productions and Marc Goucher Ltd and is inspired by the life of Marc Bolan.