Carlo Maria Mastai-Ferretti

Carlo Maria Mastai-Ferretti, also known as Pope Pius IX, was the Pope from 1846 to 1878. He is notable for being one of the longest-serving popes in history and for his influential role during a period of significant change in Europe. Pius IX initiated the First Vatican Council, which defined the doctrine of papal infallibility, asserting that the Pope is free from error when speaking on faith and morals. His papacy also witnessed the loss of the Papal States, leading to the Pope's reduced temporal power and a more spiritual focus for the Catholic Church.