Gary was born in Vilna, Russian Empire (now Vilnius, Lithuania) under the name Roman Kacew (Yiddish: קצב‎, Russian: Рома́н Ка́цев). In his books and interviews, he presented many different versions of his parents’ origins, ancestry, occupation and his own childhood. His mother, Mina Owczyńska, was a Litvak actress from Švenčionys and his father was a businessman Arieh-Leib Kacew (1883—1942) from Trakai, also a Lithuanian Jew. Arieh Leib abandoned the family in 1925 and remarried. Gary would later claim that his actual father was the celebrated actor and film star Ivan Mozzhukhin, with whom his actress mother had worked and to whom he bore a striking resemblance. Mozzhukhin appears in his memoir Promise at Dawn). When Gary was fourteen, he and his mother moved to Nice, France. Converted to Catholicism by his mother, Gary studied law, first in Aix-en-Provence and then in Paris. He learned to pilot an aircraft in the French Air Force in Salon-de-Provence and in Avord Air Base, near Bourges.  Following the Nazi occupation of France in World War II, he fled to England and under Charles de Gaulle served with the Free French Forces in Europe and North Africa. As a bombardier-observer, he took part in over 25 successful sorties, logging over 65 hours of air time. During this time, he changed his name to Romain Gary. He was greatly decorated for his bravery in the war, receiving many medals and honours, including Compagnon de la Libération and commander of the Légion d’honneur. In 1945 he published his first novel, Education européenne. Immediately following his service in the war, he worked in the French diplomatic service in Bulgaria and Switzerland. In 1952 he became the secretary of the French Delegation to the United Nations. In 1956, he became Consul General in Los Angeles. It was in this post he became acquainted with Hollywood.

Gary would become one of France’s most popular and prolific writers, authoring more than thirty novels, essays and memoirs, some of which he wrote under a pseudonym.  He is the only person to win the Prix Goncourt twice. This prize for French language literature is awarded only once to an author. Gary, who had already received the prize in 1956 for Les racines du ciel, published La vie devant soi under the pseudonym of Émile Ajar in 1975. The Académie Goncourt awarded the prize to the author of this book without knowing his real identity. A period of literary intrigue followed. Gary’s cousin’s son Paul Pavlowitch posed as the author for a time. Gary later revealed the truth in his posthumous book Vie et mort d’Émile Ajar. It was not unusual for Gary to write under an assumed name. He also published as Shatan Bogat, Rene Deville and Fosco Sinibaldi, as well as his own name Roman Kacew. In addition to his success as a novelist, he was involved in movies. He wrote the screenplay for the motion picture, The Longest Day and co-wrote and directed the film Kill! (1971), starring his now ex-wife Jean Seberg. In 1979, he was a member of the jury at the 29th Berlin International Film Festival.

Gary’s first wife was the British writer, journalist, and Vogue editor Lesley Blanch (author of The Wilder Shores of Love). They married in 1944 and divorced in 1961. From 1962 to 1970, Gary was married to American actress Jean Seberg, with whom he had a son, Alexandre Diego Gary. According to Diego Gary, he was a distant presence as a father; “Even when he was around, my father wasn’t there. Obsessed with his work, he used to greet me, but he was elsewhere.”  Being informed that Jean Seberg had an affair with Clint Eastwood, he challenged him to a duel, but Eastwood declined.  Gary died of a self-inflicted gunshot wound on 2 December 1980 in Paris, France. He left a note which said specifically that his death had no relation to Seberg’s suicide the previous year. He also stated in his note that Émile Ajar was himself.  Gary was cremated in Père Lachaise Cemetery and his ashes were scattered in the Mediterranean Sea near Roquebrune-Cap-Martin.