Taoist monk and alchemist who journeyed from China across the heartland of Asia to visit Genghis Khan, the famed Mongol conqueror, at his encampment north of the Hindu Kush mountains. The narrative of Ch'ang-ch'un's expedition, written by his disciple-companion Li Chih-chang, presents faithful and vivid representations of the land and people between the Great Wall of China and Kābul (now in Afghanistan), and between the Yellow Sea and the Aral Sea.

Ch'ang-ch'un was a member of a Taoist sect known for extreme asceticism and for the doctrine of hsing-ming, which held that man's “natural state” had been lost but could be recovered through prescribed practices. In 1188 he was invited to give religious instruction to the Juchen dynasty emperor Shih Tsung, then reigning over northern China.

In 1215 the Mongols captured Peking, and in 1219 Genghis Khan sent for Ch'ang-ch'un. He went first to Peking, and, having also received an invitation from the Khan's younger brother, Temüge, who lived in northeastern Mongolia, he crossed the Gobi Desert and visited Temüge's camp near Buir Nor. Ch'ang-ch'un arrived in Samarkand, now in Uzbekistan, in midwinter (1221–22) and reached the Khan's Hindu Kush mountain camp in the spring. He returned to Peking in 1224. The account of the journey, Hsi-yu chi (“Journey to the West”), appeared in an annotated English translation, The Travels of an Alchemist (1931), by Arthur Waley.