The Treaty of Nymphaeum was a trade and defense pact signed between the Empire of Nicaea and the Republic of Genoa in Nymphaion in March 1261. This treaty would have a major impact on both the restored Byzantine Empire and the Republic of Genoa that would later dictate their histories for several centuries to come.

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 Sea and the Black Sea. Between the 16th and 17th centuries, it was one of the major financial centers in Europe.