Reformation, the religious revolution that took place in the Western church in the 16th century. Its greatest leaders undoubtedly were Martin Luther and John Calvin. Having far-reaching political, economic, and social effects, the Reformation became the basis for the founding of Protestantism, one of the three major branches of Christianity.
The world of the late medieval Roman Catholic Church from which the 16th-century reformers emerged was a complex one. Over the centuries the church, particularly in the office of the papacy, had become deeply involved in the political life of western Europe. www.britannica.com/EBchecked/topic/495422/Reformation