Volonte was born in Milan to Mario, a soldier from Varese, and Carolina, the daughter of wealthy industrialists from Milan. The family later moved to Turin, where in 1944 her father became commander of a brigade that fought the partisans in the area. When the war ended, he was imprisoned and died in jail, while his mother was forced to sell the family property and rent out their house in order to earn some income to support the family.
The future actor had a rebellious character from childhood. At 14, he dropped out of school in order to find a job to help his mother. He spent almost two years in France and, on his return to Italy, joined a travelling acting troupe as a secretary and camera assistant. The constant contact with actors sparked his interest in the profession and in 1954 he went to Rome with the intention of enrolling at the National Academy of Drama. Three years later, while still a student, he landed his first role in a television drama and was soon hailed as one of the best actors of his generation. Volonte graduated from the Academy in 1957 and moved to Milan, where he created several roles in theatre and television.
From 1960 onwards, he began to act in films, and his first popularity came when he appeared in Sergio Leone's westerns "A Fistful of Dollars", "A Few Dollars More" and in the comedy "The Brancaleone Army". Later, Volonte turned to more serious, dramatic roles, crime films and political thrillers (the actor himself belonged to the Italian Communist Party). He played a series of roles in films by the best directors of the time - Damiano Damiani, Carlo Lizzani, Francesco Rossi - the most famous of which was the Oscar-winning Indagine su un cittadino al di sopra di ogni sospetto. The actor chose his roles carefully, always taking into account whether they were in line with his own political and life principles. Some of the most famous films in which he refused to act were Francis Ford Coppola's The Godfather and Federico Fellini's Casanova. Nevertheless, Volonte has portrayed historical figures such as Michelangelo, Caravaggio and Giordano Bruno. In 1981, he was among the candidates for the film "For Your Eyes Only", but was not confirmed
The actor also tried his hand at politics and ran in the 1992 parliamentary elections, but was unsuccessful.
Volonte died of a heart attack in Greece, while starring in the film "Ulysses' Gaze", directed by Theodoros Angelopoulos, and later replaced by Swedish actor Erland Josephson. The urn containing his ashes is buried on the island of Madalena, near Sardinia.