John XXIII, born Angelo Giuseppe Roncalli in 1881, was an Italian prelate who served as the head of the Catholic Church from 1958 until his death in 1963. After his ordination as a priest in 1904, he held several diplomatic roles, including serving as the Apostolic Nuncio to France and as a representative in Bulgaria, Turkey, and Greece. Following his appointment as a cardinal in 1953, he was elected pope, a position from which he initiated major institutional reforms.