Treaties of Locarno, series of seven agreements designed to promote the security of western Europe at the end of World War I. The treaties were signed by representatives from Belgium, Czechoslovakia, France, Germany, Great Britain, Italy, and Poland in Locarno, Switzerland, on October 16, 1925. The first of the Locarno treaties guaranteed the common boundaries of France, Germany, and Belgium. The Rhineland, an area covering parts of Belgium, France, and Germany, was established as a neutral zone. The British and Italians were involved in the guarantee, but they did not have any new military obligations to ensure the implementation of these. Although France signed security treaties with Poland and Czechoslovakia, the treaties did not offer the same frontier recognition to the countries on Germany's eastern borders. There were, however, agreements providing for the arbitration of disputes between Germany and its Belgian, French, Czech, and Polish neighbours. The treaties were to operate within the framework of the League of Nations, which Germany joined in 1926.

Initially the “spirit of Locarno” helped improve relations between France and Germany, but matters deteriorated in the 1930s. German leader Adolf Hitler denounced the principal Locarno Treaty and ordered the remilitarization of the Rhineland in 1936. Germany's aggression, unchallenged by the other signatories of the Locarno treaties, resulted in World War II.