Peter John Sinfield (born 27 December 1943) is an English poet and songwriter, most famously known as the lyricist and co-founding member of early incarnations of King Crimson, whose debut album In the Court of the Crimson King has been regarded as one of the most influential progressive rock albums ever released.

In 2005, Sinfield was noted as a "Prog rock hero" in Q magazine, for his impressive lyrical contribution and creative influence while working within the rock music industry.