A Byzantine-Mongol Alliance occurred during the end of the 13th and the beginning of the 14th century between the Byzantine Empire and the Mongol Empire. Byzantium actually tried to maintain friendly relations with both the Golden Horde and the Ilkhanate realms, who were often at war with each other. The alliance involved numerous exchanges of presents, military collaboration and marital links, but dissolved in the middle of the 14th century.

Emperor Michael VIII Palaiologos established an alliance with the Mongols, who themselves were highly favourable to Christianity, as a minority of them were Nestorian Christians. He signed a treaty in 1266 with the Mongol Khan of the Kipchak (the Golden Horde), and he married two of his daughters (conceived through a mistress, a Diplovatatzina) to Mongol kings: Euphrosyne Palaiologina, who married Nogai Khan of the Golden Horde, and Maria Palaiologina, who married Abaqa Khan of Ilkhanid Persia.