Jon Hassell (March 22, 1937 – June 26, 2021) was an American trumpet player and composer active since the 1960s. 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. He had also worked with artists such as the Theatre of Eternal Music, Talking Heads, Farafina, Peter Gabriel, Tears for Fears, Ani DiFranco, Techno Animal, Ry Cooder, Moritz von Oswald, and Carl Craig.