Treaty of Königsberg (1656)
| Type | Legal status of the Duchy of Prussia |
|---|---|
| Signed | 17 January 1656 |
| Location | Königsberg castle (now Kaliningrad) |
| Signatories | |
| Parties | |
| Language | Latin |
The Treaty of Königsberg was concluded on 7 January (O.S.) / 17 January (N.S.) 1656 during the Second Northern War. Frederick William I, the "Great Elector" of Brandenburg and duke of Prussia, was forced to join the Swedish camp and became a Swedish vassal for the Duchy of Prussia and Ermland (Ermeland, Warmia). In a second treaty, negotiated on 24 February 1656 in Königsberg (Królewiec), Frederick William I concluded a defensive alliance with France.