Chen Tuan 陳摶 (died August 25, 989[1]) was a Chinese Taoist credited with creation of the kung fu system Liuhebafa ("Six Harmonies and Eight Methods").

In Chinese, he is often respectfully referred to as "Aged Ancestor Chen Tuan" (陳摶老祖 Chén Tuán Lǎozǔ) and "Ancestral Teacher Xiyi" (希夷祖師 Xīyí Zǔshī).

Chen Tuan, styled Tunan, titled himself Fuyao Zi (one soaring upward in the high sky, from Nan Hua Jing written by Zhuangzi).

As an important teacher of Taoist doctrines who pioneered the Confucian school of idealist philosophy of the Song and Ming dynasties, he had a profound influence upon later generations.

This Taoist sage was considered the embodiment of the Supreme Lord Lao and received the nickname of "Aged Ancestor," a symbol of Taoism in Mount Hua.