Biography

Pius IX, original name Giovanni Maria Mastai-Ferretti (born May 13, 1792, Senigallia, Papal States—died February 7, 1878, Rome; beatified September 3, 2000; feast day February 7), Italian head of the Roman Catholic church whose pontificate (1846–78) was the longest in history and was marked by a transition from moderate political liberalism to conservatism. Notable events of his reign included the declaration of the dogma of the Immaculate Conception (1854), the Syllabus of Errors (1864), and the sessions of the First Vatican Council (1869–70), during which the doctrine of papal infallibility was authoritatively defined.