Julio Cortázar was born on August 26, 1914, in Brussels, Belgium, where his Argentine parents, Julio José Cortázar and María Herminia Descotte de Cortázar, were on a business trip. Once World War I began, the family was forced to remain in Europe for several years. Finally in 1918 they returned to Argentina and settled in a suburb of Buenos Aires. Cortázar's father left the family soon afterwards, and Julio and his sister were raised by their mother and aunt.

Starting at a young age, Cortázar demonstrated both a love of and aptitude for literature and received nurturing and guidance in his writing from his teachers. Cortázar received primary (1932) and secondary (1935) teaching degrees, but due to economic reasons, he was forced to cut short his studies at Universidad de Buenos Aires and begin teaching in the remote provincial towns of Bolívar and Chivilcoy. From 1944 to 1945 Cortázar taught French literature at Universidad de Cuyo, Mendoza, but in 1946 he resigned as a result of his political views and his anti-Perón demonstrations.

Back in Buenos Aires, Cortázar worked for the publishing group Cámara Argentina del Libro (1946-1948), completed a translation degree in record time, and worked as a public translator (1948-1951). During these years his short stories "Casa tomada" and "Lejana" appeared in Jorge Luis Borges' literary magazine Los Anales de Buenos Aires, and he published a theoretical work, Teoría del túnel (1947). The novel El examen, written in 1950, was initially rejected by the publisher and only released posthumously in 1986. In 1951 Cortázar published the short story collection Bestiario and began his voluntary exile from Argentina by moving to Paris. In the French capital Cortázar quickly became a translator for the United Nations Educational, Scientific and Cultural Organization (UNESCO), a position he would hold for the rest of his life.

On August 23, 1953, Cortázar married fellow Argentine translator Aurora Bernárdez. Although they divorced after twenty years, the two remained close friends. His second marriage was to Canadian writer Carol Dunlop with whom he collaborated on Los autonautas de la cosmopista: O, un viaje atemporal París-Marsella (1983), a surrealistic account of their month-long journey on the French highway.

Cortázar belonged to the "boom" generation of Latin American writers who broke new ground with their work during the 1950s and 1960s. He is perhaps most well known for the highly experimental novel Rayuela (1963) and the socio-politically based Libro de Manuel (1973). His literary production included other novels—Los premios [1960], 62: Modelo para armar [1968] and Un tal Lucas [1979]), poetry (Los reyes [1949], Pameos y meopas [1971], and Salvo el crepúsculo [1984]) and essays ( La casilla de los Morelli [1973], Argentina: Años de almabradas culturales [1984] and Nicaragua: Tan violentamente dulce [1983]—but predominately consisted of short stories: Final del juego [1950], Las armas secretas [1959], Historias del cronopios y de famas [1962], Todos los fuegos el fuego [1966], Alguien que anda por ahí y otros relatos [1977], and Queremos tanto a Glenda [1980].

Cortázar was also a frequent traveler and advocate of human rights. He was particularly concerned about the torture of political prisoners and the repressive rule of dictators in Latin America. A socialist, he supported both the Cuban and Nicaraguan revolutions. Cortázar promoted his views through speaking engagements and political essays. He also made several trips to the United States and participated in conferences at University of California, Berkeley (1980).

Cortázar died of leukemia and heart disease on February 12, 1984. He was buried in Montparnassee Cemetery alongside Carol Dunlop.