How Many?
How many ecumenical councils have been held by the Catholic Church?
Answer: 21
For a period of more than 1,600 years, the Catholic Church has assembled at ecumenical councils its patriarchs, cardinals, bishops, abbots of male religious orders, and others nominated by the pope to discuss issues of faith, church doctrine and discipline, often defining heresies within the church. The pope must approve the decisions of the council. The first was the First Council of Nicaea (or Nicea), convened in 325 after Christianity came under the protection of the Roman emperor Constantine, which produced the original Nicene Creed, still used (with some modifications) as the Christian profession of faith today. The First Lateran Council of 1123 was the first to be held after the Great Schism between the East and West; it also dealt with the First Crusade, which had begun in the late 11th century, granting remission of sins to those who participated. The longest council was the Council of Trent (1545–1563), which was overseen by three successive popes, addressed the Protestant Reformation and issued a number of its own reform decrees, popularly known as the Counter-Reformation. Only two councils have been called in modern times: The First Vatican Council (1869–1870) officially decreed the infallibility of the pontiff when speaking ex cathedra (literally, “from the chair [of Peter]”) in his office as Peter’s successor. The most recent, the Second Vatican Council (1962–1965), addressed the role of the Catholic Church in the modern world and, most notably, revised the liturgy to encourage lay participation, leading to celebration of the mass in vernacular languages rather than only Latin.