Jon Hassell was an American trumpet player and composer. He was best known for developing the concept of "Fourth World" music, which describes a "unified primitive/futurist sound" combining elements of various world ethnic traditions with modern electronic techniques. The concept was first articulated on Fourth World, Vol. 1: Possible Musics, his 1980 collaboration with Brian Eno.
Born in Tennessee, Hassell studied contemporary classical music in New York and later in Germany under composer Karlheinz Stockhausen. He subsequently worked with minimalist composers Terry Riley and La Monte Young, and studied under Hindustani singer Pandit Pran Nath. His association with Brian Eno in the early 1980s would introduce Hassell to a larger audience. He subsequently worked with musical artists such as Talking Heads, David Sylvian, Farafina, Peter Gabriel, Tears for Fears, Ani DiFranco, Techno Animal, Ry Cooder, Moritz von Oswald, and Carl Craig.