"Reformation" can refer to any one of several movements within Western Christianity:

* The Protestant Reformation started by Martin Luther in 1517, resulting in the formation of the Lutheran and Calvinist churches.
* The English Reformation started by Henry VIII resulting in the formation of the Church of England, in some aspects parallel to the Protestant Reformation.
* The Radical Reformation, attempts to conflate the ideas of the abovementioned reformations with political radicalism.
* The Counter-Reformation, an attempt by the Roman Catholic Church to end the abuses that had given rise to the Protestant Reformation, starting at the Council of Trent