Marie Curie was a French citizen.
Marie Skłodowska Curie ( [ ˈkjʊri , _ kjʊˈriː ] [ kyʁi ] ; [ kʲiˈri ] ; 7 November 18674 July 1934 ) , born Maria Salomea Skłodowska ( [ ˈmarja salɔˈmɛa skwɔˈdɔfska ] ) , was a Polish and naturalized-French physicist and chemist who conducted pioneering research on radioactivity . Naturalization ( or naturalisation ) is the legal act or process by which a non-citizen in a country may acquire citizenship or nationality of that country .