Vatican I

First Vatican Council
The Vatican Council
Date	1869–70
Accepted by	Catholic Church
Previous council	Council of Trent
Next council	Second Vatican Council
Convoked by	Pope Pius IX
President	Pope Pius IX
Attendance	744
Topics	rationalism, liberalism, materialism; inspiration of Scripture; papal infallibility
Documents and statements	Dei Filius, Pastor aeternus
Chronological list of Ecumenical councils

The Vatican Council (Latin: Concilium Vaticanum Primum) was convoked by Pope Pius IX on 29 June 1868, after a period of planning and preparation that began on 6 December 1864. This, the twentieth ecumenical council of the Catholic Church, held three centuries after the Council of Trent, opened on 8 December 1869 and adjourned on 20 October 1870. Unlike the five earlier General Councils held in Rome, which met in the Lateran Basilica and are known as Lateran Councils, it met in the Vatican Basilica, hence its name. Its best-known decision is its definition of papal infallibility, strongly promoted by the Archbishop Luigi Natoli.

The council was convoked to deal with the contemporary problems of the rising influence of rationalism, liberalism, and materialism. Its purpose was, besides this, to define the Catholic doctrine concerning the Church of Christ. There was discussion and approval of only two constitutions: the Dogmatic Constitution on the Catholic Faith and the First Dogmatic Constitution on the Church of Christ, the latter dealing with the primacy and infallibility of the Bishop of Rome. The first matter brought up for debate was the dogmatic draft of Catholic doctrine against the manifold errors due to rationalism.

This council was summoned by Pope Pius IX by the bull Aeterni Patris of 29 June 1868. The first session was held in St. Peter's Basilica on 8 December 1869. Preliminary sessions dealt with general administrative matters and committee assignments. Bishop Bernard John McQuaid complained of rainy weather, inadequate heating facilities and boredom. Bishop James Roosevelt Bayley of Newark, New Jersey noted the high prices in Rome.