pentapolis

thumb|right|The Pentapolis on the Adriatic was part of the Exarchate of Ravenna, an administrative unit of the [[Byzantine Empire.Red: The Pentapolis. Orange: Other cities of the Exarchate.]]

A pentapolis (from Greek penta-, 'five' and polis, 'city') is a geographic and/or institutional grouping of five cities. Cities in the ancient world probably formed such groups for political, commercial and military reasons, as happened later with the Cinque Ports in England.