Ferdinand I, Holy Roman Emperor
Ferdinand I governed the Austrian Habsburg lands while his brother Charles V ruled Spain, eventually succeeding him as Holy Roman Emperor in 1558. He negotiated the Peace of Augsburg (1555) with the Protestant princes, establishing the principle of cuius regio, eius religio. His reign began the separate development of the Austrian and Spanish Habsburg lines.
- Lived: 1503 CE – 1564 CE
- Nationality: austrian
- Roles: emperor, head_of_state
