In 1875 the “Convention of the Metre” was signed in Paris by representatives of seventeen nations in which they agreed to establish an international system of units based on the metre and the kilogram. The Metre Convention founded the “International Bureau of Weights and Measures (Bureau International des Poids et Mesures, BIPM)” as a permanent scientific laboratory with the task to conserve the international prototypes of the metre and kilogram and to provide comparisons between the national standards and the international prototypes in order to establish worldwide uniformity of measurements. Since 1875 metrology has become much more complex but the fundamental mission of the BIPM has not changed significantly and can still be defined as supporting worldwide uniformity of measurement. A historical review of the BIPM and its mission and role in the 21st century is presented.