The Council of Trent (Latin: Concilium Tridentinum) was an Ecumenical Council of the Catholic Church. It is considered to be one of the Church's most important councils.^[1] It convened in Trento, Italy, then the capital of the Prince-Bishopric of Trent of the Holy Roman Empire, between 13 December 1545, and 4 December 1563 in twenty-five sessions for three periods. During the pontificate of Pope Paul III, the Council fathers met for the first eight sessions in Trento (1545–47), and for the ninth to eleventh sessions in Bologna (1547).^[2] Under Pope Julius III, the Council met in Trento (1551–52) for the twelfth to sixteenth sessions, and under Pope Pius IV, the seventeenth to twenty-fifth sessions took place in Trento (1559–63).

The Council issued condemnations on what it defined as Protestant heresies at the time of the Reformation and defined Church teachings in the areas of Scripture and Tradition, Original Sin, Justification, Sacraments, the Eucharist in Holy Mass and the veneration of saints. It issued numerous reform decrees.^[3] By specifying Catholic doctrine on salvation, the sacraments, and the Biblical canon, the Council was answering Protestant disputes.^[1] The Council entrusted to the Pope the implementation of its work; as a result, Pope Pius IV issued the Tridentine Creed in 1565; and Pope Pius V issued in 1566 the Roman Catechism, in 1568 a revised Roman Breviary, and in 1570 a revised Roman Missal. Through these the Tridentine Mass was standardised (named after the city's Latin name Tridentum). In 1592, Pope Clement VIII issued a revised edition of the Vulgate Bible.^[4]

The Council of Trent, delayed and interrupted several times because of political or religious disagreements, was a major reform council; it was an embodiment of the ideals of the Counter-Reformation.^[4] More than 300 years passed until the next Ecumenical Council. When announcing Vatican II, Pope John XXIII stated that the precepts of the Council of Trent continue to the modern day, a position that was reaffirmed by Pope Paul VI.^[5]