The Peace of Westphalia in 1648 ending the Thirty Years` War(1618-1648) has been recognized as the first international treaty which formed the basis of the so-called ``Westphalian System`` based upon the concept of competing sovereign states, not the dominance of an empire. This article attempts, however, not to approach the peace of 1648 from a perspective of the history of diplomacy or international relations, but to inspect both confessional and national diversities, and long-term changes of the memory cultures. The peace treaty signed simultaneously in M?nster and Osnabr?ck had been regarded as a political victory of the Protestants around the eighteenth century. Memory cultures regarding the treaty were primarily concentrated in the Protestant territories and cities; Catholics (even in the Bishop`s city of M?nster) were long reluctant to commemorate it. Most of the central European states were involved in the diplomatic congress that put an end to the devastating war and restored the long awaited peace, which led to the diverse memory cultures on the peace of 1648. The Peace of M?nster has played an essential role in the collective memory of the Dutch, since it officially approved the independence of the Netherlands from the Spanish kingdom. The memory culture in Sweden tended to concentrate less on the peace itself than on Gustavus Adolphus, ``the Lion of the North``, who made his country one of the great military powers in early modern Europe. In spite of the acquisition of Alsace, the Peace of Westphalia has not been commemorated as the national ``lieu de memoire`` in France because it could not stop the Franco-Spanish War(1635-1659) and was overshadowed by political turbulence caused by the Fronde. In Germany the memory culture on the peace of 1648 witnessed extreme fluctuations depending on the changes of the historical milieus. It carried as a principal basis of the law and peace for the Holy Roman Empire an overwhelmingly positive connotation, before being stigmatized as ``antinational trash`` by both nationalists in the nineteenth century and the Nazis. It was not until 1945 that the Germans rediscovered the positive aspects of the peace treaty as the memory culture was gradually influenced by European integration.