The Council of Trent establishes an official distinction between Roman Catholicism and Protestantism.

The Council of Trent, held between 1545 and 1563 in Trent, 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 "most impressive embodiment of the ideals of the Counter-Reformation." It was the last time a Catholic ecumenical council was organized outside the city of Rome, & the second time to be convened in the territory of the Holy Roman Empire.

The Catholic Church, also known as the Roman Catholic Church, is the largest Christian church, with 1.27 to 1.41 billion baptized Catholics worldwide as of 2025. It is among the world's oldest and largest international institutions and has played a prominent role in the history and development of Western civilization. The Church consists of 24 sui iuris (autonomous) churches, including the Latin Church and 23 Eastern Catholic Churches, which comprise almost 3,500 dioceses and eparchies around the world, each overseen by one or more bishops. The pope, who is the bishop of Rome, is the chief pastor of the church.

Protestantism is a branch of Christianity that emphasizes justification of sinners through faith alone, the teaching that salvation comes by unmerited divine grace, the priesthood of all believers, and the Bible as the sole infallible source of authority for Christian faith and practice. The five solae summarize the basic theological beliefs of mainstream Protestantism.

January 26 is the 26th day of the year in the Gregorian calendar; 339 days remain until the end of the year.