Benedetti was born in Paso de los Toros in the department of Tacuarembó in a family of Italian descent. In 1946 he married Luz López Alegre.

From 1973 to 1985, when a military dictatorship ruled Uruguay, Benedetti lived in exile in Buenos Aires, Lima, Havana, and Spain. Following the restoration of democracy, he divided his time between Montevideo and Madrid. He has been granted Honoris Causa doctorates by the Universidad de la República, Uruguay, the Universidad de Alicante, Spain, and the Universidad de Valladolid, Spain. In 1986 he was awarded Laureate Of The International Botev Prize. On June 7, 2005, he was named the recipient of the Premio Menéndez y Pelayo. His poetry was also used in the 1992 Argentine movie The Dark Side of the Heart (El lado oscuro del corazón) in which he read some of his poems in German.

On January 26, 2006, Mario Benedetti joined other internationally renowned figures such as Gabriel García Márquez, Ernesto Sábato, Thiago de Mello, Eduardo Galeano, Carlos Monsiváis, Pablo Armando Fernández, Jorge Enrique Adoum, Pablo Milanés, Luis Rafael Sánchez, Mayra Montero and Ana Lydia Vega, in demanding sovereignty for Puerto Rico. The request for the recognition of Puerto Rico's independence was obtained at the behest of the Puerto Rican Independence Party.

He died in Montevideo on 17 May 2009. He had suffered from respiratory and intestinal problems for more than a year.

Before dying, he dictated to his personal secretary, Ariel Silva what would become his last poem :

Mi vida ha sido como una farsa

Mi arte ha consistido

En que esta no se notara demasiado

He sido como un levitador en la vejez

El brillo marrón de los azulejos

Jamás se separó de mi piel

(Fragment)

A free translation into English of these few lines might be as follows:

My life has been like a sham

My art has consisted

Of not being too noticed

I've been just as hovering during my old age

The brown sheen of the bluebirds

Has never detached itself from my skin

(Fragment)

For his poetry and novels Benedetti had won numerous international awards. The Truce, first published in 1960, has since been translated into 19 languages and made into two motion pictures. Each year below links to either the corresponding "[year] in literature" or "[year] in poetry" article:

Poetry

• 1945:La víspera indeleble ("Indelible Eve"), his first published book
• 1956: Poemas de oficina ("Office Poems")
• 1963:
• Inventario, Poesía 1950–1958 ("Inventory, Poems 1950–1958")
• Poemas del hoyporhoy ("Poems of Today")
• 1977: La casa y el ladrillo ("The House and the Brick")
• 1981: Viento del exilio ("Air From Exile")
• 1986: Preguntas al azar ("Random Questions")
• 1988: Yesterday y mañana ("Yesterday and Tomorrow")
• 1991: Las soledades de Babel ("The Loneliness of Babel")
• 1994: Inventario dos (1985-1994) ("Inventory Two (1985-1994)"), published in Madrid
• 1995: ("The Exercise of Discretion: Oblivion Is Full of Memory"), published in Spain
• 1996: El amor, las mujeres y la vida. Poemas de amor.
• 1997: La vida ese paréntesis
• 2002: Insomnios y Duermevelas, ISBN 84-7522-959-X
• 2004: Defensa propia, ISBN 950-731-438-5
• Little Stones At My Window (Bilingual edition; translation and introduction by Charles Hatfield) ISBN 1-880684-90-X
• Poemas de otros
• Noción de Patria
• Sólo mientras tanto
• Quemar las naves
• A ras de sueño
• Letras de emergencia

Short stories

• 1960: Montevideanos
• Aquí se respira bien
• Los pocillos
• Acaso irreparable
• Escrito en Überlingen
• El reino de los cielos
• Miss Amnesia
• "Una carta de amor"
• La noche de los feos
• "La sirena viuda"
• "El buzón del tiempo"

Essays

• 1960: El país de la cola de paja
• "La Colección"

Novels

• 1953: Quién de nosotros
• 1960: La tregua, the basis for a 1974 film of the same name
• 1965: Gracias por el fuego, the basis for a 1984 film of the same name
• 1971: El cumpleaños de Juan Ángel
• 1982: Primavera con una esquina rota
• 1982: Vientos del exilio
• 1984: Geografías
• 1991: Las soledades de Babel
• 1993: La borra del café
• 1996: Andamios
• 2003: El porvenir de mi pasado

Plays

• 1958: Ida y Vuelta
• 1979: Pedro y el capitán

Miscellaneous

• 1969: Book Cubano, including poems, articles and interviews about Cuba and his experiences there
• 1996: Obras completas ("Complete Works"), in 28 volumes, published in Argentina