William Pierce Butler is an American multi-instrumentalist and composer. He is best known as a former member of the indie rock band Arcade Fire, with whom he recorded six studio albums. Butler was a member of the band for eighteen years, between 2003 and 2021, and played synthesizer, bass, guitar and percussion. He is known for his spontaneity, energy and antics during live performances and is the younger brother of Arcade Fire frontman Win Butler. In 2010, he won a Grammy Award for Album of the Year as part of Arcade Fire.