Ginzburg was born in Odessa to a Jewish family, and moved with them to Turin at a very young age. He studied at the Massimo d’Azeglio liceo in Turin Liceo classico Vincenzo Gioberti. This school molded a group of intellectuals and political activists that would fight Benito Mussolini's Fascist regime and, eventually, help create the post-war democratic Italy. His classmates included such notable intellectuals as Norberto Bobbio, Piero Gobetti, Cesare Pavese, Giulio Einaudi, Massimo Mila, Vittorio Foa, Giancarlo Pajetta and Felice Balbo.
In the early 1930s, Ginzburg taught Slavic Languages and Russian Literature at the University of Turin, and was credited with helping to introduce Russian authors to the Italian public. In 1933, Ginzburg co-founded, with Giulio Einaudi, the publishing house Einaudi. He lost his teaching position in 1934, having refused to swear an oath of allegiance imposed by the Fascist regime.
Soon after this, he and 14 other young Turinese Jews, including Sion Segre Amar, were arrested for complicity in the so-called "Ponte Tresa Affair" (they were carrying anti-fascist lietrature over the border from Switzerland), but Ginzburg's sentence was light. He was arrested again in 1935 for his activities as leader (with Carlo Levi) of the Italian branch of Giustizia e Libertà, the Justice and Freedom Party, which Carlo Rosselli had founded in Paris in 1929.
In 1940, the Ginzburgs received the fascist punishment known as confino, or internal exile, to a remote, impoverished village, in their case Pizzoli in the Abruzzi, where they stayed from 1940-1943. Somehow, Leone was able to continue his work as head of the Einaudi publishing house throughout the period. In 1942, he co-founded the clandestine Partito d'Azione or "Action Party", a party of the democratic resistance. He also edited their newspaper L'Italia Libera.
In 1943, after the Allied invasion of Sicily and the fall of Mussolini, Leone went to Rome, leaving his family in the Abruzzi. When Nazi Germany invaded in September, Natalia Ginzburg and their three children fled Pizzoli, simply climbing aboard a German truck and telling the driver that they were war refugees who had lost their papers. They met with Leone and went into hiding in the capital; twenty days later, Leone Ginzburg was arrested in Rome, this time by the Gestapo. They subjected him to severe torture in the German section of the Roman prison, Regina Coeli. He died there from the injuries he received.