Khaidu was a Mongol man from the Borjigin clan who, according to the Secret History of the Mongols, became the first man to rule all the Mongol clans.
According to the Secret History of the Mongols, a bluish wolf and his mate, a fallow deer, settled at the head of the Onon River, and there, Bat Tsagaan, the ancestor of the Mongols, was born. Many generations passed, and different clans emerged from the line of Batacaciqian. In the Borjigin clan there was a man named Khaidu. One day a rival clan attacked and killed his family and destroyed their hard earned prosperity. In revenge, Khaidu gathered a large group and defeated his rivals. Khaidu earned a large following, and according to the Secret History, became the first to rule all the Mongol clans; Khaidu Khan. Khaidu Khan is also a direct ancestor to Genghis Khan. Khabul Khan was Khaidu's most famous great-grandson.