Socialist Unity was a Trotskyist group in the United States. It was founded by former members of the Socialist Workers Party (SWP) in 1985, around Les Evans who wanted to maintain links with the United Secretariat of the Fourth International. Immediately after being expelled from the SWP, future Socialist Unity supporters formed part of the Socialist Action but left that grouping in favor of joining the Solidarity with the International Socialists and Workers Power in 1986. Within Solidarity they constituted a Fourth International Caucus which retains links with the United Secretariat of the Fourth International in this capacity.