Izquierda Unida (United Left) is an electoral coalition that was organized in 1986 during the mobilizations in Spain against NATO. It was formed by several groups of leftists, green, left-wing socialists, republicans, but always dominated by the Communist Party of Spain (PCE). At the present time, only the PCE continues forming and organizing IU.

After the electoral fall of the PCE in 1982 (from 10% to 3%), IU was little by little improving the results until reaching in 1993 9% (1,800,000 votes) and 1996 10.5% (2,600,000 votes). As of 1999 it began to decay, lowering in 2000 to 5% (only 1,250,000 votes). In those elections it signed a pact with the Socialist Party (PSOE).

From 1986 to 2001, its leader was the general secretary of the PCE, Julio Anguita. From 2001 on it has been Gaspar Llamazares. IU has an important support in Andalusia (mainly in Seville, Córdoba, and Málaga), in Asturias, Madrid, Valencia, and in the Basque Country.

See also: Politics of Spain