Rukn ad-Din Baibars Bundukdari (died July 1, 1277) was a Mameluk sultan of Egypt in the 13th century.
Baibars was a commander of the Mameluks in Egypt around 1250, when he defeated the Seventh Crusade of Louis IX of France. He was still a commander under Sultan Qutuz at the Battle of Ain Jalut in 1260. After the battle he killed Qutuz and took power for himself, and began an assault on the Crusader Principality of Antioch, which had attempted to ally with the Mongols against Baibars at Ain Jalut. In 1263 he attacked Acre, the capital of the remnant of the Kingdom of Jerusalem, but was unable to take it. Nevertheless, he defeated the Crusaders in many minor battles; whenever possible he took as prisoners members of the Knights Templar and Knights Hospitaller, whom he considered to be the greatest threats to his power.
In 1266 Baibars defeated the Armenians in Cilicia, the only powerful ally of Antioch. In 1268 he besieged Antioch, capturing the city on May 18. He razed the city and killed or enslaved the population, although Prince Bohemund was able to escape. The fall of Antioch led to a brief Crusade in 1271 led by Edward I of England, who also attempted to ally with the Mongols, although they were unable to capture any territory from Baibars. Although Edward and Baibars settled a truce, Baibars tried to have Edward killed by the Hashshashin, and Edward returned home in 1272.
Baibars then fought with the Seljuk Turks in Anatolia, who were by this time subjects of the Mongols. Throughout his reign Baibars attempted to avoid another battle with the stronger Mongol force, and he retreated from Seljuk territory before Mongol reinforcements arrived. He died in Syria in 1277.