The Battle of Varna took place on November 10, 1444 near Varna in eastern Bulgaria. In this battle the Ottoman Empire under Sultan Murad II defeated the Polish and Hungarian armies under Wladislaus III of Poland (Władysław III Warneńczyk in Polish) and Janos Hunyadi.

After a failed expedition in 1441/1442 against Belgrade, the Ottoman sultan Murad II signed a ten-year truce with Hungary. After he had made peace with the Karaman Emirate in Anatolia in August 1444, he resigned the throne to his 12-year-old son Mehmed II.

Despite the peace treaty, Hungary co-operated with Venice and the pope Eugenius IV to organize a new crusader army. On this news Murad was recalled to the throne by his son. Although Murad initially refused this summoning persistently on the grounds that he was not the sultan anymore, he was outwitted by his son who on the news of his refusal wrote to him: "If you are the sultan, lead your armies; but if I am the sultan, I hereby order you to come and lead my armies." Murad then had no choice but to reclaim the throne.

A mixed Christian army consisting mainly of Hungarian and of Polish forces, but with detachments of Czechs, papal knights, Bosnians, Croatians, Serbs, Bulgarians, Romanians and Ruthenians, met with a numerically superior force of Ottoman Turks. The Hungarians were ill-equipped, and promised support from Wallachia, Albania and Constantinople did not arrive. They had promises from Venetians that their fleet would not allow Turkish army to cross the Bosphorus. The 30,000 Crusaders were overwhelmed by 30,000 Turks. Over half of the soldiers from the united army perished.

The defeat ended any serious attempts to prevent the conquest of eastern Europe by Turks for several decades and the death of Wladyslaw III in the battle left Hungary in the hands of the four-year-old Ladislaus Posthumus of Bohemia and Hungary.