The Metre Convention was signed in Paris on 20 May 1875. Its stated purpose was to assure the international unification and perfection of the metric system. At its origin was a set of recommendations made at a Conference on geodesy held in Berlin in 1867 which called for the manufacture of a new European prototype of the metre and the creation of a European international bureau of weights and measures. The response of the French Government was to create an International Metre Commission to consider the question. The Commission duly recommended what the Berlin Conference had proposed and a Diplomatic Conference on the Metre took place in Paris. It opened on 1 March 1875 and culminated on 20 May in the signing of the Metre Convention by the representatives of 17 States. Included in the Convention was the creation of an International Bureau of Weights and Measures, a General Conference on Weights and Measures and an International Committee for Weights and Measures. The international organization comprising these three organs still exists and is the means through which Governments today arrange for and support the International System of Units, SI, the successor to the metric system. This article gives a brief description of the discussions and events surrounding all this.