A gendarmerie () is a military force with law enforcement duties among the civilian population. The term gendarme (English: ) is derived from the medieval French expression gens d'armes, which translates to "rural police" or "men-at-arms" (literally, "armed people"). In France and some Francophone nations, the gendarmerie is a branch of the armed forces that is responsible for internal security in parts of the territory (primarily in rural areas and small towns in the case of France), with additional duties as military police for the armed forces. It was introduced to several other Western European countries during the Napoleonic conquests. In the mid-twentieth century, a number of former French mandates and colonial possessions (such as Lebanon, Syria, the Ivory Coast and the Republic of the Congo) adopted a gendarmerie after independence. A similar concept exists in Eastern Europe in the form of Internal Troops, which are present in many countries of the former Soviet Union and its former allied countries.

Some of the more prominent modern gendarmerie organizations include the French National Gendarmerie, French National Guard, Spanish Civil Guard, the Romanian Jandarmeria, Algerian National Gendarmerie, Argentine National Gendarmerie, United States Constabulary, Burkinese National Gendarmerie, Italian Carabinieri, Chilean Carabineros, Moldovan Carabinieri, Royal Netherlands Marechaussee, the Royal Moroccan Gendarmerie, the Portuguese National Republican Guard, Serbian Žandarmerija, Mexican National Guard, Tunisian National Guard, Turkish Gendarmerie and the Royal Canadian Mounted Police/Gendarmerie royale du Canada.