Zhenyuan Daxian (Chinese: 镇元大仙; lit. 'The Great Immortal Zhenyuan'), also known as Zhenyuanzi (Chinese: 镇元子), is a character from the 16th century Chinese novel Journey to the West and a Taoist deity who is the patriarch of all Earth's Immortals in Taoist pantheon.^[1][2] His residence is Wanshoushan Wuzhuang Guan, one of the only two officially listed Dongtianfudi in Journey to the West.^[3][4]

According to Journey to the West, Zhenyuan Daxian is based in Wuzhuang Temple (五莊觀) on Longevity Mountain (萬壽山) in Aparagodānīya [zh]. In his temple, there is a special Ginsengfruit (人參果) tree that was formed when primeval chaos was first being divided, before the separation of Heaven and Earth. The fruit of the tree is known as "Grass-returning Cinnabar" or "manfruit". The tree produces only 30 fruits every 9,000 years and is shaped like an infant less than three days old. Just by smelling the fruit, a person can extend his lifespan by 360 years; a person who eats the fruit can live an additional 47,000 years. Zhenyuan and Tang Sanzang had been friends in Tang Sanzang's previous life as Golden Cicada (Chinese: 金蟬子), a disciple of the Buddha. Soon, upon the protagonists' arrival at his temple during their journey, he was invited by Yuanshi Tianzun to listen. However, he had instructed his servants Qingfeng (清風; literally "Clear Wind") and Mingyue (明月; literally "Bright Moon") to give two fruits to Tang Sanzang. Tang Sanzang is frightened when he sees that the fruit looks like a premature infant and refuses to eat it. Qingfeng and Mingyue eat the fruits themselves and are seen by Zhu Bajie. Sun Wukong, however, steals another three fruits for himself and his two juniors. When Qingfeng and Mingyue realize that some of the fruits are missing, they accuse Sun Wukong of theft and call the pilgrims names. Sun Wukong destroys the Ginseng fruit tree in anger and escapes with his companions. When Zhenyuan returns to his temple, he is furious after learning the truth from Qingfeng and Mingyue. He pursues the protagonists and captures them twice after they attempt to flee again. Later he agrees not to punish them if Sun Wukong can find a way to revive the tree.^[5][6]

Sun Wukong visited the Sanxing and many high deities in the heavenly court, but none of them knew how to revive the tree. Finally, he went to Guanyin and told her what had happened. Guanyin says,

"You have no conscience at all. That manfruit tree of his is the life-root from the time when Heaven and Earth were separated, and Great Immortal Zhenyuan is the Patriarch of the Earth's Immortals, which means even I have to show him a certain respect."

The conflict is eventually resolved when Guanyin helps them restore the Ginseng fruit tree back to life. Zhenyuan is so pleased that he gives up his desire for revenge and becomes sworn brothers with Sun Wukong. He treats all of them to a fruit feast before seeing them off on their journey.^[5][7]

According to the descriptions in the novel, Zhenyuan Daxian is the great god who interacts with the Three Pure Ones, indicating his incredibly esteemed status. A couplet hung outside his Daoist temple reads, "Longevity like the immortals, a household with the same lifespan as heaven," suggesting an extraordinary level of longevity. Sun Wukong, who has seen much of the world, naturally finds this claim hard to believe, saying, "Five hundred years ago, when I caused a ruckus in the Heavenly Palace, I never heard such words at Laozi's gate." Furthermore, Wuzhuang Temple doesn't venerate the Three Pure Ones, the Four Sovereigns, or other celestial authorities; they only offer incense to "heaven and earth". According to the two attendants, Qingfeng and Mingyue, only one word, "heaven," deserves the incense of Zhenyuan Daxian, while the word "earth" isn't worthy. Additionally, Zhenyuan Daxian refers to the Three Pure Ones as his friends, the Four Sovereigns as acquaintances, Jiuyao (九曜, nine heavenly deities) as juniors, and the Origin Stars (元辰) as guests. This leads to questions about the true identity of Zhenyuan Daxian.^[8]

Qing dynasty Daoist hermit Wang Xiangxu [zh] stated: "Within the sleeves of Zhenyuan Daxian, the universe resides, vast and capable of encompassing all beings. Yet, it cannot capture those who move freely. Even if it could, they would escape, and if captured again, they would break free once more, just as if never ensnared. The universe may be immense, but the heart within is even greater. With this heart, one can transcend the boundaries of the universe. Although referred to as puppets, who among them truly controls whom?".^[9]