The treaty that ended the Thirty Years' War in Europe is the Treaty of Westphalia, concluded in 1648. This series of agreements marked the end of a devastating war primarily fought in the Holy Roman Empire, which involved numerous European powers. The treaty recognized the sovereignty of various states and allowed for greater religious tolerance, marking a significant shift in the political landscape of Europe. It laid the groundwork for the modern nation-state system and altered the balance of power among European countries.