The Peace of Westphalia
Sovereign states agree not to interfere in each other's internal affairs.
- When
- Known to
- ± 1 year
- Era
- Early Modern, Holocene
The settlement of 1648 ends the Thirty Years' War through the first genuinely multilateral European congress, recognising the right of rulers to determine religion within their own territories and treating states as formally equal sovereign entities. Whether it created the modern international system or merely acknowledged it is debated by historians, but Westphalian sovereignty remains the shorthand for the principle, and it underlies international law today.