The Morean war, also known as the Sixth Ottoman–Venetian War, was fought between 1684–1699 as part of the wider conflict known as the "Great Turkish War", between the Republic of Venice and the Ottoman Empire. Military operations ranged from Dalmatia to the Aegean Sea, but the war's major campaign was the Venetian conquest of the Morea (Peloponnese) peninsula in southern Greece. On the Venetian side, the war was fought to avenge the loss of Crete in the Cretan War (1645–1669). It happened while the Ottomans were entangled in their northern struggle against the Habsburgs – beginning with the failed Ottoman attempt to conquer Vienna and ending with the Habsburgs gaining Buda and the whole of Hungary, leaving the Ottoman Empire unable to concentrate its forces against the Venetians. As such, the Morean War was the only Ottoman–Venetian conflict from which Venice emerged victorious, gaining significant territory. Venice's expansionist revival would be short-lived, as its gains would be reversed by the Ottomans in 1718.

The Peloponnese, Peloponnesus or Morea is a peninsula and geographic region in Southern Greece, and the southernmost region of the Balkans. It is connected to the central part of the country by the Isthmus of Corinth land bridge which separates the Gulf of Corinth from the Saronic Gulf. From the late Middle Ages until the 19th century, the peninsula was known as the Morea, a name still in colloquial use in its demotic form.