Federico Fellini nicknamed him "Snaporaz" while they are working on La Dolce Vita (1960); 20 years later this was the name of the character he played in City of Women (1980).
Co-starred with former lover Catherine Deneuve in four films: It Only Happens to Others (1971), Liza (1972), L'événement le plus important depuis que l'homme a marché sur la lune (1973), and Don't Touch the White Woman! (1974). Twenty years after their relationship ended, they both appeared in the ensemble production Les cent et une nuits de Simon Cinéma (1995).
Cohabited with Faye Dunaway for two years after they met on the set of A Place for Lovers (1968). [1968-1970].
Cohabited with Anna Maria Tatò. [1976-1996].
During his studies at the Centro Universiatio Teatrale, he got to know Luchino Visconti, who gave him a role in "Un Tram che si chiama desiderio" (A Streetcar Named Desire) under his direction. At that time, he also met Anna Magnani and Federico Fellini.
Father of Chiara Mastroianni and Barbara Mastroianni
Former father-in-law of Benjamin Biolay.
From 1971 to 1975 he had an intense relationship with french actress Catherine Deneuve. She was at his bedside when he died, along with their daughter, Chiara Mastroianni.
Grandchildren: Milo (b. 1996) and Anna (b. 2003).
He is buried in the Cimitero Monumentale del Verano in Rome, Italy.
His three Oscar nominations for Divorce Italian Style (1961), A Special Day (1977), and Dark Eyes (1987) are the record for a performer in a foreign language film. The only other performers with multiple Oscar nominations for foreign language films are Sophia Loren, Liv Ullmann and Isabelle Adjani with two each.
Older brother of film editor Ruggero Mastroianni, who edited several of Marcello's films directed by Federico Fellini
Per a Mastroianni biographer, his mother revealed shortly before her deathbed that she was a Jewish immigrant from Belarus, a heritage she had previously hidden.
Since 1998, a "Marcello Mastroianni Award" is given to the best "first time" young actor/actress at the Venice Film Festival.
Son of Annibale Ninchi twice: La Dolce Vita (1960) and 8½ (1963).
Told interviewers that Federico Fellini hired him for La Dolce Vita (1960) because he had a "terribly ordinary face".
Uncle of Federica Mastroianni.
Visited the genius Sergei Parajanov at his house in Tbilisi, Georgia, Soviet Union in 1980s and then, in July of 1990, along with Federico Fellini, Tonino Guerra and Bernardo Bertolucci wrote: "With the death of Sergei Paradjanov cinema lost one of its magicians".