Medieval communes in the European Middle Ages had sworn allegiances of mutual defense (both physical defense and of traditional freedoms) among the citizens of a town or city. They took many forms, and varied widely in organization and makeup. Communes are first recorded in the late 11th and early 12th centuries, thereafter becoming a widespread phenomenon. They had the greater development in central-northern Italy, where they were real city-states based on partial democracy.

The English and French word "commune" appears in Latin records in various forms. The classical Latin communio means an association. In some cases the classical Latin commune was used to mean people with a common interest. Ultimately, the roots are cum (with or together) + munire (to wall), literally 'to wall together' (i.e., a shared fortification). More frequently the Low Latin communia was used from which the Romance commune was derived. When independence of rule was won through violent uprising and overthrow, they were often called conspiratio.