Count Alexandre de Marenches (1921- ) was a French military officer.

He was head of the Service de Documentation Extérieure et de Contre-Espionnage (SDECE, France's external intelligence agency) from November 6, 1970 to June 12, 1981.

In 1986, he co-authored Dans le secret des Princes ("In the Princes' secret", literally, published in English as The Evil Empire: Third World War Continues) with journalist Christine Ockrent about his days working in secret services.

In 1992, he co-authored The Fourth World War: Diplomacy and Espionage in the Age of Terrorism with David Andelman .