Igor Gouzenko

| birth_place = Dmitrov, Moscow Governorate, Russian SFSR | name = | image = Igor Gouzenko 1946.jpg | caption = Gouzenko in 1946 | native_name = Игорь Сергеевич Гузенко | image size = 200px | death_date = | death_place = Mississauga, Ontario, Canada | known = Exposing Soviet spy ring in Canada | signature = Gouzenko sign.png | alias = George Brown | nationality = Russian, Canadian | occupation = Cipher clerk }}

Igor Sergeyevich Gouzenko (; January 26, 1919 – June 25, 1982) was a cipher clerk for the Soviet embassy to Canada in Ottawa, Ontario, and a lieutenant of the Soviet Main Intelligence Directorate (GRU). He defected on September 5, 1945, three days after the end of World War II, with 109 documents on the USSR's espionage activities in the West. In response, Canada's Prime Minister, Mackenzie King, called a royal commission to investigate espionage in Canada.

Gouzenko exposed Soviet intelligence's efforts to steal nuclear secrets as well as the technique of planting sleeper agents. The "Gouzenko Affair" is often credited as a triggering event of the Cold War, with historian Jack Granatstein stating it was "the beginning of the Cold War for public opinion" and journalist Robert Fulford writing he was "absolutely certain the Cold War began in Ottawa". Granville Hicks described Gouzenko's actions as having "awakened the people of North America to the magnitude and the danger of Soviet espionage". Provided by Wikipedia