Marcantonio Giustinian was the 107th Doge of Venice, reigning from his election on 26 January 1684 until his death. Giustiniani was the quintessential Doge of the Republic of Venice, taking little interest in affairs of state. He had little role in the conduct of the Morean War (1684-1699), which was raging during his time as Doge, though a number of military victories were secured by provveditore Francesco Morosini, who would later be Giustinian's successor as Doge.

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.