Möngke Khan (Мөнх хаан), also transliterated as Mongke, Mongka, Möngka, Mangu or Mangku (; c. 1208 – 1259), was the fourth Great Khan of the Mongol Empire from 1251 to 1259. He was the son of Tolui and Sorghaghtani Beki, brother of Hulagu, and a grandson of Genghis Khan.

Möngke is noted as participating in the European campaign of 1236-1242, in the campaign against the Kypchaks and Maghas, the destruction of Kiev, and the assault of Hungary. In the summer of 1241, before the premature end of the campaign, Möngke returned home.

After the death of the third Great Khan, Güyük, Möngke found himself the champion of the factions of Genghis' descendants who aimed to supplant the branch of Ögedei. Batu, the senior male of the family, had almost come to open warfare with Güyük in 1248, the khan's early death precluding this. Batu joined forces with Tolui's widow to outmaneuver the regent, Ögedei's widow Oghul Ghaimish. Batu called a kurultai in Siberia in 1250, which was protested as not being in Mongolia proper. However, Batu ignored the opposition, had his brother Berke call a kurultai within Mongolia, and elected Möngke khan in 1251.

Realizing they had been outmaneuvered, the Ögedeiid faction attempted to overthrow Möngke under the pretext of paying him homage, but their conspiracy was clumsy and easily avoided. Oghul Ghaimish was sewn up into a sack and drowned.

Möngke, as khan, seemed to take much more seriously the legacy of world conquest he had inherited than did Güyük. He concerned himself more with the war in China, outflanking the Song Dynasty through the conquest of Yunnan in 1254 and an invasion of Indochina, which allowed the Mongols to invade from north, west, and south. Taking command personally late in the decade, he captured many of the fortified cities along the northern front. These actions ultimately rendered the conquest a matter of time. He dispatched his brother Hulagu to the southwest, an act which was to expand the Mongol Empire to the gates of Egypt. European conquest was neglected due to the primacy of the other two theaters, but Möngke's friendliness with Batu ensured the unity of empire.

However, while conducting the war in China at Fishing Town in modern-day Chongqing, Möngke died nearby the site of the siege on August 11, 1259. There are several different accounts as to how he perished. One was was killed by an arrow shot from a Chinese archer during the siege. Other accounts claim that he was killed by dysentery or even a cholera epidemic. In any case, his death forced Hülegü to abort his campaign in Syria and Egypt, and caused a civil war that destroyed the unity and invincibility of the Mongol Empire.

In some texts Möngke is said to be killed by a rock falling onto his head while attacking Fishing Town, while other texts said Mongke died of an illness or injury when attacking Fishing Town. In popular text, famous Chinese novelist Jin Yong dramatized the death of Mongke Khan in his popular Condor Trilogy series (The Return of the Condor Heroes, 1959), which describes a lovelorn young Song soldier by the name Yang Guo (); who had to serve in national defense duties during the Mongol attacks against Song China, and became a reluctant hero who happened to be the triggerman of the shot that killed Mongke Khan. Nevertheless, Mongke was the only Great Khan to have ever been killed in action.

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