The Metre Convention (French: Convention du Mètre), also known as the Treaty of the Metre, is an international treaty that was signed in Paris on 20 May 1875 by representatives of 17 nations (Argentina, Austria-Hungary, Belgium, Brazil, Denmark, France, Germany, Italy, Peru, Portugal, Russia, Spain, Sweden and Norway, Switzerland, Ottoman Empire, United States of America, and Venezuela). The treaty created the International Bureau of Weights and Measures (BIPM), an intergovernmental organization under the authority of the General Conference on Weights and Measures (CGPM) and the supervision of the International Committee for Weights and Measures (CIPM), that coordinates international metrology and the development of the metric system.

As well as founding the BIPM and laying down the way in which the activities of the BIPM should be financed and managed, the Metre Convention established a permanent organizational structure for member governments to act in common accord on all matters relating to units of measurement.

The three organs of the BIPM are:

The General Conference on Weights and Measures (Conférence générale des poids et mesures or CGPM) – the plenary organ of the BIPM which consists of the delegates of all the contracting Governments;

The International Committee for Weights and Measures (Comité international des poids et mesures or CIPM) – the direction and supervision organ of the BIPM that is made of 18 prominent metrologists from 18 different member states;

The headquarters or secretariat of the BIPM which is located at Saint-Cloud, France. The secretariat employs around 70 people and hosts BIPM's formal meetings.Only states can be Members as per the Metre Convention. In addition to Member status, the General Conference on Weights and Measures (CGPM) created in 1999 the status of Associate of the CGPM open to States and Economic Entities to enable them to participate in some activities of the BIPM through their National Metrology Institutes (NMIs). Membership of the convention requires payment of substantial fees. Failure to pay these over a span of years, without any expectation of a payment agreement, has caused a number of nations such as North Korea to be removed from the protocol. As of 13 January 2020, there are 62 member states and 40 associate states and economies.

Initially the Metre Convention was only concerned with the units of mass and length but, in 1921, at the 6th meeting of the General Conference on Weights and Measures (CGPM), it was revised and it extended the scope and responsibilities of the BIPM to other fields in physics. In 1960, at the 11th meetings of the CGPM, the system of units it had established was named the International System of Units, with the abbreviation SI.