Comacchio (Italian: ; Comacchiese: Cmâc' ) is a town and comune of Emilia Romagna, Italy, in the province of Ferrara, 48 kilometres (30 mi)  from the provincial capital Ferrara. It was founded about two thousand years ago; across its history it was first governed by the Exarchate of Ravenna, then by the Duchy of Ferrara, and eventually returned to be part of the territories of the Papal States. For its landscape and its history, it is considered one of the major centres of the Po delta.
 Comacchio is situated in a lagoon just north of the present mouth of the Reno. It is built on more than thirteen different islets, joined by bridges. The most important resources of these wetlands are the fish farming and the salt ponds. The seaport of Porto Garibaldi lies 7 kilometres (4 mi) to the east. The wetlands south of the town, the Valli di Comacchio, are classified as a Site of Community Importance and a Special Protection Area in Italy. They are also rated internationally important by the Ramsar Convention for the conservation and sustainable use of wetlands.
 The etymology of the town's name is uncertain (Greek-Latin cumaculum meaning "small wave"; "grouping of bumps" in Etruscan). The foundation is attributed to the Etruscans, who were already settled in the Po delta: the Etruscan city of Spina rose near Comacchio.
 After its early occupation by the Etruscans and the Gauls, when the site lay on the main stream of the River Po, Comacchio was annexed by Rome. Under Emperor Augustus, who ruled Rome from 27 BC to AD 14, a canal was dug to deepen its lagoon. Part of the original wetlands were drained and divided among villae rusticae.
 Comacchio enjoyed prosperity under the Goths and the Lombards, and became the seat of a Lombard duchy. It owed its fortunes to its salt pans and its strategic importance to its location: when the Lombard king Authari expanded the Lombard dominion at the expense of Byzantium, he took the fortress of Comacchio and cut off communication between Padua and Ravenna. When the Franks descended into northern Italy in 756, their king, Pepin the Short, included Comacchio in his famous donation of land to Pope Stephen II, a grant later confirmed by Pepin's son and successor, Charlemagne. In 854 Comacchio was sacked by their rivals in the salt trade, the Venetians, who laid it waste in 946. Saracen raiders burned the city in 876, but despite this Comacchio slowly recovered. The Holy See later acquired the city and presented it to the archbishopric of Ravenna.
 In 1299, Emperor Rudolph I conferred it on Obizzo IV d'Este of Ferrara. In 1508 it became Venetian, but in 1597 was claimed by Clement VIII as a vacant fief. In 1598 the Papal States again acquired Comacchio and retained it until 1866 when it became a part of the Kingdom of Italy. The spread of malaria made the site unhealthy. Since then, most of the swamp land has disappeared, leaving ground for the expansion of agriculture, and creating new zones for dwellings.
 The area was the scene of fierce fighting during Operation Roast, which occurred in the last months of the World War II.
 Comacchio was formerly the seat of a bishopric and retains its cathedral, now a co-cathedral in the Archdiocese of Ferrara-Comacchio.
 The town was once home to a factory for sugar refining, which closed in 1988. Comacchio and its seafront Lidi are a centre for tourism. The town is noted in Italy for its practice of eel-fishing in the nearby wetlands, and many dishes served in Comacchio revolve around eel.
 The historical residential zone stood on small islands connected to each other: for this reason, the bridges are the defining element of the historic centre of Comacchio.
 Comacchio is known for its seven lidos, with its wide sandy shores spreading throughout the coast, from the mouths of the Reno river to the Po di Volano river, crossing the regional park of Po delta. They are, from northern to southern:
 The oldest of them is Porto Garibaldi; the most recently established is Lido di Volano.
 Tourism is one of the main activities in its seven lidos, especially during summer. Other prominent activities are commercial fishing, aquaculture and fish farming. In the past, salt production was also very important, whose trade had been causing bitter disputes with the Serenissima Republic of Venice.
 Comacchio is appreciated for having kept intact most of its architecture over time: canals, ancient buildings and monumental bridges are elements that give it the typical appearance of the northern lagoon cities (for example, Chioggia and other cities of the Venetian lagoon). For this reason, it is also known as the Little Venice.