movement in Spanish and Spanish American poetry after World War I, characterized by a tendency to use free verse, complicated metrical innovations, and daring imagery and symbolism instead of traditional form and content. Influenced by the emphasis on form of the French Symbolists and Parnassians, a distinguished coterie of avant-garde poets (ultraístas) produced verse that often defied objective analysis and gave the impression of a coldly intellectual experimentation. Launched in Madrid in 1919 by the poet Guillermo de Torre, Ultraism attracted most of the important contemporary poets. Their works were published chiefly in the two major avant-garde periodicals, Grecia (1919–20) and Ultra (1921–22).

Jorge Luis Borges (Borges, Jorge Luis) introduced Ultraism to South America in 1921. There the movement attracted poets such as the Chileans Pablo Neruda (Neruda, Pablo) and Vicente Huidobro (Huidobro, Vicente) and the Mexican poets Jaime Torres Bodet (Torres Bodet, Jaime) and Carlos Pellicer. Although the movement had subsided by 1923, the sociopolitical overtones of much of the writing of the South American ultraístas, as seen in the verse of César Vallejo (Vallejo, César) of Peru, flowered into the Marxist poetry of the following decade. Later the verbal techniques of the ultraístas were revived by post-World War II avant-garde writers.