Pope Pius XII ( ) , born Eugenio Maria Giuseppe Giovanni Pacelli ( ; 2 March 1876 -- 9 October 1958 ) , reigned from 2 March 1939 to his death in 1958 .
XII '' ) , born Eugenio Maria Giuseppe Giovanni Pacelli ( March 2 , 1876 -- October 9 , 1958 ) , was an Italian priest of the Roman Catholic Church and the 261st Pope from 1939 to 1958 .