Otherwise known as the Religious Peace of Augsburg. This was the peace treaty which finalised the establishment of Protestantism in the Holy Roman Empire. Officially it only recognised Lutheranism but in practice it came to allow all Protestant sects.

It allowed the ruler of each state to chose Roman Catholicism or Lutheranism - `cuius regio, eius religio'.

This was the final nail in the coffin of hopes for Religious unity in the HRE.