The Venetian navy (Venetian: Armada) was the navy of the Venetian Republic which played an important role in the history of the republic and the Mediterranean world. It was the premier navy in the Mediterranean Sea for many centuries between the medieval and early modern periods, providing Venice with control and influence over trade and politics far in excess of the republic's size and population. It was one of the first navies to mount gunpowder weapons aboard ships, and through an organised system of naval dockyards, armouries and chandlers was able to continually keep ships at sea and rapidly replace losses. The Venetian Arsenal was one of the greatest concentrations of industrial capacity prior to the Industrial Revolution and responsible for the bulk of the republic's naval power.

Driven at first by a rivalry with the Byzantine Empire, and later the maritime republics of Pisa and Genoa for primacy over trade with the Levant, the Venetian navy was at times technically innovative and yet operationally conservative. With the final fall of Constantinople it played a key role in checking the maritime advance of the Ottoman Empire for over three centuries. The navy's long decline mirrored that of the republic, beginning in the 16th century and ending with the capitulation of the city to Napoleon in 1797.

Giving shelter to refugees fleeing Hunnic invaders in the 6th century, Venice grew in the Venetian Lagoon in the northern Adriatic. From the very beginning, it focused on establishing and maintaining maritime trade routes across the Eastern Mediterranean to the Levant and beyond; Venice's commercial and military strength, and continued survival, was founded on the strength of its fleet. This allowed it for centuries to check the maritime advance of the numerically superior forces of the Ottoman Empire.

The origins of the Venetian navy lay in the traditions of the Roman and Byzantine navies. Before developing into the Empire's archnemesis, Venice was originally a vassal, later an ally of the Byzantine Empire and it utilised Byzantine naval and military techniques. At this time there was little difference between the merchant and naval fleets; all ships had to be able to defend themselves if the need arose. In the event of hostilities ships and crews were taken up from trade to reinforce the war fleet, being dispersed back to the pursuit of commerce on the ending of the emergency. Even so, there were two types of vessels one primarily military and one predominantly mercantile.

Towards the end of the 9th century there appeared the main instrument of Venetian power:

In addition a number of other types of ships are mentioned in the Chronicles,

With these ships, Venice fought alongside the Byzantines against the Arabs, Franks and Normans, winning by the year 1000 dominance of the Adriatic, subjugating the Narentines and taking control of Dalmatia, the first domain in what would become Venice's Stato da Màr.

Towards the end of this period Venice had accumulated a large and powerful fleet. Although still nominally a vassal of the Byzantine Empire, Venice was increasingly independent and a rival of the Byzantines for primacy in the Eastern Mediterranean. Rather than depending on the Byzantines for their survival, the Venetians held, with their fleet, the balance of power, and was able to use it to leverage concessions from both the Byzantines and their rivals in Western Christendom, profiting from both. In return for Venetian aid against the Normans, in the Byzantine–Norman wars, Alexios I Komnenos the Byzantine Emperor granted the Venetians far-reaching commercial privileges in the Chrysobull, or Golden Bull, of 1082.