Adolfo Bioy Casares (Spanish pronunciation: [aˈðolfo ˈβjoj kaˈsaɾes]; 15 September 1914 – 8 March 1999) was an Argentine fiction writer, journalist, diarist, and translator.

He was born in Recoleta, a neighborhood of Buenos Aires traditionally inhabited by upper-class families, where he would reside the majority of his life.

Under the pseudonyms H. Bustos Domecq and Benito Suárez Lynch, the two teamed up on a variety of projects from short stories (Seis problemas para don Isidro Parodi, Dos fantasías memorables, Un modelo para la muerte), to screenplays (Los orilleros, Invasión), and fantastic fiction (Antología de la literatura fantástica, Cuentos breves y extraordinarios).

Between 1945 and 1955, they directed "El séptimo círculo" ("The Seventh Circle"), a collection of translations of popular English detective fiction, a genre that Borges greatly admired.

In 2006, Borges, a biographical volume of more than 1600 pages from Bioy Casares' journals, revealed many additional details of the friendship shared by the two writers.

The novel's introduction was written by Borges, in which he comments on the absence of precursors to science fiction in Spanish literature, presenting Bioy Casares as the pioneer of a new genre.

In 1954, one of Bioy Casares' mistresses gave birth in the United States to his daughter, Marta, who was subsequently adopted by his wife Silvina.

Dictionary of Argentinean slang Letters Diaries Works written in collaboration with Jorge Luis Borges Dos fantasías memorables and Un modelo para la muerte were originally published in private printings of only 300 copies.