Genghis Khan (born Temüjin; 1162 – 25 August 1227), also known as Chinggis Khan, was the founder and first khagan of the Mongol Empire, which later became the largest contiguous land empire in history. Having spent the majority of his life uniting the Mongol tribes, he launched a series of military campaigns that conquered large parts of China and Central Asia.
Born between 1155 and 1167 and given the name Temüjin, he was the oldest child of Yesugei, a Mongol chieftain of the Borjigin clan, and his wife Hoelun of the Olkhonud clan. Yesugei died when Temüjin was eight, and his family was abandoned by their tribe in the Mongol steppe. Temüjin gradually built up a small following and allied with Jamukha and Toghrul, two other Mongol chieftains, in campaigns against other Mongol tribes. Due to the erratic nature of the sources, this period of Temüjin's life is uncertain; he may have spent this time as a servant of the Jin dynasty. The alliances with Jamukha and Toghrul failed completely in the early 13th century, but Temüjin was able to defeat both individuals and claim sole rulership over the Mongol tribes. He formally adopted the title "Genghis Khan" at a kurultai in 1206.
With the tribes fully united, Genghis set out on a campaign of conquest. Having vassalised the Western Xia state by 1211, he then invaded the Jin dynasty in northern China, forcing the Jin emperor Xuanzong to abandon the northern half of his realm in 1214. In 1218, Qara Khitai, a Central Asian khanate, was annexed by Mongol forces, allowing Genghis to lead an invasion of the neighbouring Khwarazmian Empire in the following year. The invading Mongols toppled the Khwarazmian state and devastated the regions of Transoxiana and Khorasan, while another expedition penetrated as far as Georgia and Kievan Rus'. In 1227, Genghis died while besieging the rebellious Western Xia; his third son and heir Ögedei succeeded him to the throne two years later.
The Mongol military campaigns begun by Genghis saw widespread destruction and millions of deaths across Asia and Eastern Europe.