In the winter of 1226–27, Genghis Khan fell from his horse while hunting and became increasingly sick. His illness slowed the progress of a siege against Xia. Despite advice to return home and recover, he insisted on continuing. Genghis died on August 25, 1227, but his death was kept secret. The Xia city, unaware of his death, fell the next month. The population suffered severe brutality, leading to the near extinction of the Xia civilization. There's speculation about how Genghis died. Some sources suggest illness like malaria or bubonic plague, while others claim he was shot by an arrow or struck by lightning.

After his death, Genghis was buried near Burkhan Khaldun peak in the Khentii Mountains, a site he had chosen earlier. Details of his funeral were kept private. When his son Ogedei became khan in 1229, the grave was honored with offerings and the sacrifice of thirty maidens. Some theories suggest he may have been buried in the Ordos region to prevent decomposition.