Wèi Bóyáng 魏伯陽 was the traditional Eastern-Hàn author of the Zhōu yì cān tóng qì 周易參同契 (“Token for the Agreement of the Three in the Zhōu yì”) — the foundational alchemical-correlative classic that became the Urtext of Chinese alchemy, both wài dān 外丹 and (especially from Sòng onward) nèi dān 內丹. His historicity is debated; Gě Hóng’s Shén xiān zhuàn gives a brief hagiography. He is named as originator in many later alchemical texts, including KR5c0286 Wèi Bóyáng qī fǎn dān shā jué.