Born out of the Renaissance's critical thinking, Papal luxury and over a hundred years of festering religious argument, the Reformation shattered the ideals of Christian unity. The Protestant Reformation began in 1517 as a reaction to perceived abuses in the Catholic Church, while a Catholic Counter-Reformation emerged in the mid 16th century. Bitter division and war followed.
Overview of the Reformation
A one page introduction to the Protestant Reformation.
Origin of the word Protestant
An explanation of how this word originated.
Sources for Reformation Europe
The best listing of Reformation primary sources on the web.