19. The Council of Trent, 1545-63 A.D.

The Council of Trent, held between 1545 and 1563 in Trent (or Trento), now in northern Italy, was the 19th ecumenical council of the Catholic Church. Prompted by the Protestant Reformation at the time, it has been described as the embodiment of the Counter-Reformation.

The Council issued key statements and clarifications of the Church's doctrine and teachings, including scripture, the biblical canon, sacred tradition, original sin, justification, salvation, the sacraments, the Mass, and the veneration of saints and also issued condemnations of what it defined to be heresies committed by proponents of Protestantism.

The Council met for twenty-five sessions between 13 December 1545 and 4 December 1563. Pope Paul III, who convoked the Council, oversaw the first eight sessions (1545–47), while the twelfth to sixteenth sessions (1551–52) were overseen by Pope Julius III and the seventeenth to twenty-fifth sessions (1562–63) by Pope Pius IV. More than three hundred years passed until the next ecumenical council, the First Vatican Council, was convened in 1869.