(Nov. 10, 1444), Turkish victory over a Hungarian force, ending the European powers' efforts to save Constantinople (now Istanbul) from Turkish conquest and enabling the Ottoman Empire to confirm and expand its control over the Balkans.

In the early 1440s Ulászló I (Władysław III Warneńczyk), the king of Hungary (who was also Władysław III of Poland), sponsored a campaign against Sultan Murad II of the Ottoman Empire to reduce the Turkish threat to Constantinople and to restore Serbia to its prince, George Branković. The Hungarian forces, commanded by Hunyadi (Hunyadi, János), were supported by Pope Eugenius IV and allied with Prince George as well as with Prince János Vlad of Walachia. Together they compelled Murad to conclude a 10-year truce (June 1444), by which he restored a tributary Serbian state and pledged not to cross the Danube River.

Nevertheless, Ulászló, influenced by the pope's legate Julian Cesarini, soon took advantage of the sultan's preoccupation in Anatolia by breaking the truce and renewing his campaign against the Ottomans. Hunyadi resumed his command only with reluctance, and Prince George refused to join Ulászló's crusade. Reinforced only by a Walachian contingent, the Hungarian army marched to Varna, where on Nov. 10, 1444, it clashed with Murad, who had returned from Anatolia with a force three times larger than Ulászló's. Although the Hungarians gained an initial advantage, the Turks eventually killed Ulászló, almost annihilating the Christian army, and forced Hunyadi to flee.

Following the battle, Poland remained without a king for three years. Unhindered by further major interference from the central European powers, the Turks extended their control over the Greek rulers in the Peloponnese, who had cooperated with the crusaders. The Turks also conquered Constantinople (1453) and reabsorbed Serbia (by 1459).