The Council of Trent (Latin: Concilium Tridentinum) was an Ecumenical Council of the Roman Catholic Church. It is considered to be one of the Church's most important councils. It convened in Trent (then capital of the Prince-Bishopric of Trent of the Holy Roman Empire, in Italy) between December 13, 1545, and December 4, 1563 in twenty-five sessions for three periods. Council fathers met for the first through eighth sessions in Trent (1545–7), and for the ninth through eleventh sessions in Bologna (1547) during the pontificate of Pope Paul III. Under Pope Julius III, the council met in Trent (1551–52) for the twelfth through sixteenth sessions. Under Pope Pius IV, the seventeenth through twenty-fifth sessions took place in Trent (1559–63).

The council issued condemnations on what it defined as Protestant heresies 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. By specifying Catholic doctrine on salvation, the sacraments, and the Biblical canon, the Council was answering Protestant disputes. 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, thus standardizing what since the 20th century has been called the Tridentine Mass (from the city's Latin name Tridentum), and Pope Clement VIII issued in 1592 a revised edition of the Vulgate.