The Blessed Pope Pius IX (13 May 1792 – 7 February 1878), born Giovanni Maria Mastai-Ferretti, was the longest reigning Pope in Church history, serving from 16 June 1846 until his death, a period of nearly 32 years. During his pontificate, he convened the First Vatican Council in 1869, which decreed Papal infallibility. The Pope defined the dogma of the Immaculate Conception of the Virgin Mary, meaning that Mary was conceived without original sin and that she lived a life completely free of sin.