The Republic of Genoa was a medieval and early modern maritime republic from the years 1099 to 1797 in Liguria on the northwestern Italian coast. During the Late Middle Ages, it was a major commercial power in both the Mediterranean and Black Sea. Between the 16th and 17th centuries, it was one of the major financial centres of Europe.

Throughout its history, the Genoese Republic established numerous colonies throughout the Mediterranean and the Black Sea, including Corsica from 1347 to 1768, Monaco, Southern Crimea from 1266 to 1475, and the islands of Lesbos and Chios from the 14th century to 1462 and 1566, respectively. With the arrival of the early modern period, the Republic had lost many of its colonies, and shifted its focus to banking. This was successful for Genoa, which remained a hub of capitalism, with highly developed banks and trading companies.

Genoa was known as la Superba ("the Superb One"), la Dominante ("The Dominant One"), la Dominante dei mari ("the Dominant of the Seas"), and la Repubblica dei magnifici ("the Republic of the Magnificents"). From the 11th century to 1528, it was officially known as the Compagna Communis Ianuensis and from 1580 as the Serenìscima Repùbrica de Zêna (Most Serene Republic of Genoa). From 1339 until the state's extinction in 1797, the ruler of the republic was the doge, originally elected for life, after 1528 elected for terms of two years; in practice, the republic was an oligarchy ruled by a small group of merchant families, from whom the doges were selected.

The Genoese navy played a fundamental role in the wealth and power of the Republic over the centuries and its importance was recognized throughout Europe. To this day, its legacy as a key factor in the triumph of the Genoese Republic is still recognized, and its coat of arms is depicted in the flag of the Italian Navy. In 1284, Genoa fought victoriously against the Republic of Pisa in the Battle of Meloria for dominance over the Tyrrhenian Sea, and it was an eternal rival of Venice for dominance in the Mediterranean as a whole.

The republic began when Genoa became a self-governing commune in the 11th century and ended when it was conquered by the French First Republic under Napoleon and replaced with the Ligurian Republic. The Ligurian Republic was annexed by the First French Empire in 1805; its restoration was briefly proclaimed in 1814 following the defeat of Napoleon, but it was annexed by the Kingdom of Sardinia in 1815.

From the 11th century to 1528 it was officially known as the Compagna Communis Ianuensis and from 1580 as the Serenìscima Repùbrica de Zêna (the Most Serene Republic of Genoa) or also Repubblica di Genova (Latin: Res Publica Ianuensis, Ligurian: Repúbrica de Zêna). It was nicknamed by Petrarch as La Superba, in reference to its glory and impressive landmarks. For over eight centuries the republic was also known as la Dominante ('The Dominant one'), la Dominante dei mari ('the Dominant of the Seas'), and la Repubblica dei magnifici ('the Republic of the Magnificents').

After the fall of the Western Roman Empire, the city of Genoa was invaded by Germanic tribes, and, in about 643, Genoa and other Ligurian cities were captured by the Lombard Kingdom under the King Rothari. In 773 the Kingdom was annexed by the Frankish Empire; the first Carolingian count of Genoa was Ademarus, who was given the title praefectus civitatis Genuensis. During this time and in the following century Genoa was little more than a small centre, slowly building its merchant fleet, which was to become the leading commercial carrier of the Western Mediterranean. In 934–35 the town was thoroughly sacked and burned by a Fatimid fleet under Ya'qub ibn Ishaq al-Tamimi. This has led to discussion about whether early tenth-century Genoa was "hardly more than a fishing village" or a vibrant trading town worth attacking.

In the year 958, a diploma granted by Berengar II of Italy gave full legal freedom to the city of Genoa, guaranteeing the possession of its lands in the form of landed lordships. At the end of the 11th century the municipality adopted a constitution, at a meeting consisting of the city's trade associations (compagnie) and of the lords of the surrounding valleys and coasts. The new city-state was termed a Compagna Communis. The local organization remained politically and socially significant for centuries. As late as 1382, the members of the Grand Council were classified by both the compagnia to which they belonged as well as by their political faction ("noble" versus "popular").