The Peace of Westphalia, which brought to a close the Thirty Years War, is arguably the most important treaty signed before the twentieth century. It was a signal event of the early modern era, thoroughly of its time even as it prefigured the radical political developments of subsequent centuries. This sweeping, exhaustively researched history is the first comprehensive account of the treaty and its wider significance to appear in the English language. Bringing together the latest scholarship with an engaging narrative, it retraces the European situation leading up to the Congress of Westphalia, exploring its political and intellectual underpinnings and placing it in a broad global and chronological context. In doing so, it definitively fills a massive lacuna in the scholarly literature while offering fascinating insights into the long historical transition to modernity.