The maritime republics (Italian: repubbliche marinare) of the Mediterranean Basin were thalassocratic city-states which flourished in Italy and Dalmatia during the Middle Ages. The best known among the maritime republics are Venice, Genoa, Pisa, Ragusa, and Amalfi. Less known are Gaeta,Ancona,Noli.
From the 10th to the 13th centuries they built fleets of ships both for their own protection and to support extensive trade networks across the Mediterranean, giving them an essential role in the Crusades.
The maritime republics were city-states. They were generally republics in that they were formally independent, though most of them originated from territories once formally belonging to the Byzantine Empire (the main exceptions being Genoa and Pisa). During the time of their independence, all these cities had similar (though not identical) systems of government, in which the merchant class had considerable power.
The maritime republics were heavily involved in the Crusades, providing transport and support but most especially taking advantage of the political and trading opportunities resulting from these wars. The Fourth Crusade, originally intended to liberate Jerusalem, actually entailed the Venetian conquest of Zara and Constantinople.