The two islands that make up Chioggia were a safe refuge for the Veneto population when they were subjected to barbarian invasions in the 5th century.
Chioggia and Sottomarina were not prominent in antiquity, although they are first mentioned in Pliny as the fossa Clodia. Local legend attributes this name to its founding by a Clodius, but the origin of this belief is not known. The name of the town has changed often, being Clodia, Cluza, Clugia, Chiozza and Chioggia
The port role explains the origin of the city and the reasons for its significant development between the 11th and 12th centuries when it had already assumed the role of an important port city, developed around the salt, trade salt, fishing and other economic activities related to its the sea.
Chioggia was recognized by the Serenissima Republic a specific level of managerial, administrative and legal autonomy. This role was punctually reflected in the Pactum Clugiae, a document which guaranteed the city by the government of the Republic also its own well-defined territory. Venice enhanced the port activities of the city, and especially its defensive structures facing the sea - the direction from which most threats would arrive.
But the aggression of the Serenissima against the Clodiense maritime trade, after a few centuries, forced Chioggia into an alliance with Genoa.
The economic rivalry between those two great medieval maritime republics was resolved by the Naval War of Chioggia (1378–81), and formally ended in 1381 with the Peace of Turin.
This maritime war, with the victory of Venice, for many centuries still bent the commercial vitality of Chioggia, reduced to a fishing port Salt producer and small traffic with the Istrian and Dalmatian shores.
The Venetians rebuilt the town immediately and they strengthened it with even more defensive works, many by Michele Sanmicheli (1484-1559), who built walls and fortifications. These include the 14th century Forte di San Felice.
Unlike Venice, Chioggia did not quickly recover its prosperous pre-war conditions and throughout the 15th century it was engaged to implement an economic-social and demographic recovery.
The rebirth of the city gradually became problematic, especially due to the negative economic situation that troubled the production of salt Clugie (produced at Chioggia).
The number and size of the salt pans of Chioggia, which previously occupied very large lagoon spaces, decreased.
In this period, lagoon fishing acquired a very important role in Chioggia and the city gradually developed an ever better propensity for maritime trade in the eastern Mediterranean. Thanks to the increase in a suitable and well-prepared flotilla, maritime traffic became increasingly intense and profitable, in the wake of the great traders of the Venetian Republic. The flourishing in Chioggia of traffic and maritime trade also corresponded to the birth of great navigators and traders, like Giovanni Caboto and Nicolò de'Conti. It should also be remembered that in Chioggia the construction of boats has an ancient and glorious tradition that has historically found a prestigious social and religious response in the Mariegola dei Calafati, a statute which, dating back to 1211, represents in Italy of the municipal period one of the most ancient and complete corporate systems of arts and crafts.
With the fall of Venice (to Napoleon) Chioggia was then subjected to French rule (1797) and after to Austrian, until 1866, when it entered in the Kingdom of Italy.
The beginning of Venice's decline as a powerful maritime Republic was the end of the Port of Chioggia.
Fishing is historically the livelihood of the port, but the Port of Chioggia, besides being the seat of one of the main fishing port of Italy (ranking second after Marzara del Vallo), with a lively wholesale market, has achieved good levels of productivity and competitiveness also in break bulk, project cargoes and in the passenger traffic with small-sized cruise ships.