The treaty that ended the Thirty Years' War was the Peace of Westphalia, which was signed in 1648. This series of treaties concluded years of extensive conflict across Europe, primarily involving various German states, France, Sweden, and Spain. The Peace of Westphalia is significant as it marked a turning point in European diplomacy, establishing principles of state sovereignty and non-interference in the domestic affairs of nations. It laid the groundwork for the modern nation-state system and significantly impacted the political landscape in Europe, shifting power dynamics and helping to end religious wars on the continent.