Volonté was born in Milan but grown up in Turin, his father Mario was a fascist officer from Saronno (province of Varese), who in 1944 was in command of the Brigata Nera of Chivasso, near Turin. His mother, Carolina Bianchi, belonged to a wealthy Milanese industrial family and his younger brother Claudio was an actor too. He went to Rome to train for an acting career at the Accademia Nazionale di Arte Drammatica Silvio D'Amico, which he left in 1957. He had a brief career in television and acting in Shakespeare and Goldoni plays on the stage, before establishing his film career.

Volonté made his debut in 1960 in Sotto dieci bandiere, directed by Duilio Coletti. Just four years later, he played "Ramón Rojo" in A Fistful of Dollars (1964), and "El Indio" in For a Few Dollars More (1965), both for cash reasons as he did not consider either role serious. Both films were directed by the then-unknown Sergio Leone, and Volonté's roles in them would bring him his greatest recognition from American audiences. He played Carlo Levi in Cristo si è fermato a Eboli (1979), which was based on Levi's autobiographical account of his years in internal-exile in Aliano, south Italy, in the 1930s. The English title is Christ Stopped at Eboli. Volonté played the memorable role of the Bandito-turned-guerrilla, El Chucho, in A Bullet for the General (1966).

Volonté's performances as memorable but neurotic characters, or as a gifted leader of brigands or Revolutionaries, together with the unexpected, worldwide success of the films, gave him international fame. Volonté had already played comedies, including A cavallo della tigre (1961), by Luigi Comencini, and confirmed his versatility in L'armata Brancaleone (1966). However, he found his main dimension in dramatic roles for Banditi a Milano (1968), by Carlo Lizzani, Sbatti il Mostro in prima pagina (1972) by Marco Bellocchio, La Classe operaia va in paradiso (1972) by his friend Elio Petri and Il sospetto (1975) by Francesco Maselli.

In 1968, Volonté won a Silver Ribbon as best actor for A ciascuno il suo, also directed by Elio Petri. Volonté received the same award for two other performances: Petri's Indagine su un cittadino al di sopra di ogni sospetto (1971, winner of an Academy Award as best foreign film), considered by many to be his finest; and in The Abyss (1989).

Volonté was a strong political Activist and known for his pro-Communist leanings. In 1981, he helped terrorist Oreste Scalzone to flee from capture in Italy to Denmark. He was the partner of Italian Actress Carla Gravina for almost 10 years after they met when they played Romeo and Juliet in a theatre production in 1960. The two had a daughter Giovanna, born in the early 1960s. Actress Angelica Ippolito was his companion from 1977 until his death in 1994.

In 1983 he won the award for Best Actor at the 1983 Cannes Film Festival for La Mort de Mario Ricci. Four years later, at the 37th Berlin International Film Festival, he won the Silver Bear for Best Actor for Il caso Moro. 1988 Cannes Film Festival Official Selection, remarkable play as a Renaissance physician in The Abyss by André Delvaux from Marguerite Yourcenar's famous novel. In 1990, Volonté was named Best European Actor for Porte aperte. In 1991, at the Venice Film Festival, he won a Golden Lion for his career as a whole. Volonté played numerous roles outside Italy.

Volonté died from a heart attack in 1994 at Florina, Greece, during the filming of Ulysses' Gaze, directed by Theo Angelopoulos. Actor Erland Josephson replaced him in the role. Volonté's resting place is a small cemetery on the Sardinian island of Isola della Maddalena.