Pope Innocent III (; born Lotario de' Conti di Segni; 22 February 1161 – 16 July 1216) was the head of the Catholic Church and sovereign of the Papal States from 8 January 1198 until his death in 1216.
Pope Innocent was one of the most powerful and influential of the medieval popes. He exerted a wide influence over the Christian states of Europe, claiming supremacy over all of Europe's kings. He was central in supporting the Catholic Church's reforms of ecclesiastical affairs through his decretals and the Fourth Lateran Council. This resulted in a considerable refinement of Western canon law. He is furthermore notable for using interdict and other censures to compel princes to obey his decisions, although these measures were not uniformly successful.
Innocent greatly extended the scope of the Crusades, directing crusades against Muslim Iberia and the Holy Land as well as the Livonian Crusade against the Baltic and Finnic pagans of Livonia and the Albigensian Crusade against the Cathars in southern France. He organized the Fourth Crusade of 1202–1204, which ended in the sack of Constantinople. Although the attack on Constantinople went against his explicit orders, and the Crusaders were subsequently excommunicated, Innocent reluctantly accepted this result, seeing it as the will of God to reunite the Latin and Eastern Orthodox Churches. In the event, the sack of Constantinople and the subsequent period of Frankokratia heightened the hostility between the Latin and Greek churches; the Byzantine Empire was restored in 1261, albeit in a much weaker state.
Biography
Early life
Lotario de' Conti was born in Gavignano, near Anagni, southeast of Rome. was from the family of the counts of Segni, who eventually produced nine cardinals and four popes, including Gregory IX, Alexander IV, and Innocent XIII. Lotario's mother, Clarissa Scotti (Romani de Scotti), was according to some scholars related to Pope Clement III.
Lotario received his early education in Rome, probably at the Camaldolese Benedictine abbey of Sant'Andrea al Celio under Peter Ismael. He studied theology in Paris under the theologians Peter of Poitiers, Melior of Pisa, and Peter of Corbeil, and (possibly) jurisprudence in Bologna, according to the Gesta (between 1187 and 1189). As pope, Lotario was to play a major role in the shaping of canon law through conciliar canons and decretal letters. The work was very popular for centuries, surviving in more than 700 manuscripts. Although he never returned to the complementary work he intended to write, On the Dignity of Human Nature, Bartolomeo Facio (1400–1457) took up the task writing De excellentia ac praestantia hominis.
Election to the papacy
thumb|Arms of Innocent III at [[Santo Spirito in Sassia, Rome]]
Celestine III died on 8 January 1198. Before his death he had urged the College of Cardinals to elect Giovanni di San Paolo as his successor, but Lotario de' Conti was elected pope in the ruins of the ancient Septizodium, near the Circus Maximus in Rome after only two ballots on the very day on which Celestine III died. He was only thirty-seven years old at the time.
Reassertion of papal power
thumb| [[Bulla (seal)|Bulla of Innocent III ]]
As pope, Innocent III began with a very wide sense of his responsibility and his authority. During Innocent III's reign, the papacy was at the height of its powers. He was considered the most powerful person in Europe at the time. In 1198, Innocent wrote to the prefect Acerbius and the nobles of Tuscany expressing his support of the medieval political Sun and Moon allegory. His papacy asserted the absolute spiritual authority of his office, while still respecting the temporal authority of kings.
There was scarcely a country in Europe over which Innocent III did not in some way or other assert the supremacy which he claimed for the papacy. He excommunicated King Alfonso IX of León for marrying a near relative, Berengaria of Castile, contrary to the laws of the Church, and effected their separation in 1204. He received Aragon in vassalage from Peter II and crowned him king at Rome in 1204.
The Muslim recapture of Jerusalem in 1187 was to him a divine judgment on the moral lapses of Christian princes. He was also determined to protect what he called "the liberty of the Church" from inroads by secular princes. This determination meant, among other things, that princes should not be involved in the selection of bishops. It was particularly focused on the Patrimony of Saint Peter, the section of central Italy claimed by the popes and later called the Papal States. The patrimonium was routinely threatened by the Holy Roman Empire of the House of Hohenstaufen, which claimed it. Emperor Henry VI expected his infant son Frederick to bring Germany, Italy, and Sicily under a single ruler, which would leave the Papal States exceedingly vulnerable.
In 1201, the pope openly espoused the side of Otto IV, whose family had always been opposed to the house of Hohenstaufen.