REFORMATION, PROTESTANT. The term Reformation refers in general to the major religious changes that swept across Europe during the 1500s, transforming worship, politics, society, and basic cultural patterns. One key dimension was the Protestant Reformation, the movement that began in 1517 with Martin Luther's critique of doctrinal principles and church actions in Germany and that led to the establishment of new official churches—the Lutheran, the Reformed or Calvinist, and the Anglican.