Mario Monicelli was born in Viareggio in Tuscany and was the youngest son of the journalist Tommaso Monicelli. His older brother Giorgio worked as writer and translator. Another older brother, Franco, was a journalist. He attended studies in the local lyceum, and entered into the film world through his friendship with Giacomo Forzano, son of the playwright Giovacchino Forzano, who had been put in charge of the founding of cinema studios in Tirrenia by Benito Mussolini. Monicelli lived a carefree youth, and many of the cinematic jokes he later shot in Amici Miei were inspired from his own experience. Mario Monicelli made his first short in 1934, in collaboration with his friend Alberto Mondadori. He followed this work up with the silent film I ragazzi della Via Paal (an adaptation of the novel The Paul Street Boys), which was an award-winner in the Venice Film Festival. His first feature length work was made in 1937 (Pioggia d’estate, “Summer Rain”). In the years 1939–1942 Monicelli also produced numerous screenplays (up to 40), and worked as an assistant director. Monicelli made his official debut as a director in 1949, with Totò cerca casa, along with Steno. From the very beginning of his career Monicelli’s cinematic style had a remarkable flow to it. The duo produced eight successful movies in four years, including Guardie e ladri (1951) and Totò a colori (1952). From 1953 onwards Monicelli worked alone, without leaving his role as a writer of screenplays.

Mario Monicelli’s career include some of the masterpieces of Italian cinema. In I soliti ignoti (Big Deal on Madonna Street) (1958), now featuring the ubiquitous comedian Totò in a side role, he discovered the comical talent of Vittorio Gassman and Marcello Mastroianni and probably started the new genre of the modern commedia all’italiana. While better known in the English-speaking world under the title Big Deal on Madonna Street, the actual translation from the Italian is “the usual unknown perpetrators” (closely resempling the famous line from Casablanca: “Round up the usual suspects”). The film was nominated for the Best Foreign Language Film at the 31st Academy Awards. La Grande Guerra (The Great War), released one year later, is generally regarded as one of his most successful works, which rewarderd Monicelli with a Leone d’Oro in the Venice Film Festival, and an Academy Award nomination for the Best Foreign Film. The film, featuring Gassman and the other superstar of Italian comedy, Alberto Sordi, excelled in the absence of rhetorical accents (the tragedy of World War I was still very present to Italian’s minds in these years) and for its sharp, tragicomical sense of history. Monicelli received two more Academy Award nominations with I compagni (The Organizer, 1963) and The Girl with the Pistol (1968). L’armata Brancaleone (For Love and Gold, 1966) is another masterpiece of Italian cinema. The film tells the tragicomic tale of a Middle Age Italian knight, of uncertain nobility and few means, but high ideals, self-confidence and pomposity (Vittorio Gassman). The bizarre Macaronic Latin-Italian dialogues were devised by Age & Scarpelli, the most renowned writers of Italian comedies, and represent a whole linguistic invention which was followed by Brancaleone alle Crociate (Brancaleone at the Crusades) in 1970, and less successfully in Bertoldo, Bertoldino e Cacasenno.

Amici miei (My Friends, 1975), featuring Ugo Tognazzi and Philippe Noiret, was one of the most successful films in Italy and confirmed Monicelli’s genius in mixing humour, irony and bitter understanding of human condition. The film was popular to the point that some lines are today turned into well established idiomatic expression (“la supercazzola”), and even a programming language (“monicelli”) has been created using a syntax based on film quotes. His 1976 film Caro Michele won him the Silver Bear for Best Director at the 26th Berlin International Film Festival. The dramatic accents were predominant in the Un borghese piccolo piccolo (A Very Little Man, 1978), but left room again to more cheerful comedy and attention to historical events from a popular, intimate point of view with Il Marchese del Grillo (1981). Both films featured Alberto Sordi at his best, the latter leading Monicelli to his third Silver Bear for Best Director award at the 32nd Berlin International Film Festival.

Among the final works by Mario Monicelli are Speriamo che sia femmina (1985), Parenti serpenti (1992) and Cari fottutissimi amici (1994), featuring Paolo Hendel. The latter won an Honourable Mention at the 44th Berlin International Film Festival. His 1999 film Dirty Linen was entered into the 21st Moscow International Film Festival. His last feature film was The Roses of the Desert (Le rose del deserto, 2006), which he directed when he was 91 years old. In 1991 he received the Golden Lion for Career of the Venice Film Festival. A documentary made by Roberto Salinas and Marina Catucci, Una storia da ridere, breve biografia di Mario Monicelli, appeared in 2008. Mario Monicelli worked also for television and theatre, occasionally as an actor, and was a noteworthy playwrighter. Besides those already mentioned, actors who were launched by Monicelli or took part in his movies include Monica Vitti, Anna Magnani, Giancarlo Giannini, Stefania Sandrelli, Vittorio De Sica, Sophia Loren, Enrico Maria Salerno, Gian Maria Volontè, Paolo Villaggio, Nino Manfredi and Enrico Montesano. Monicelli died on 29 November 2010 at the age of 95. He committed suicide by jumping from a window of the San Giovanni Hospital in Rome, where he was admitted a few days earlier for prostate cancer. He was an outspoken atheist.