Bái Yùchán 白玉蟾 (1194–1229) — born Gě Chánggēng 葛長庚, also styled Hǎi qióng zǐ 海瓊子 — was the fifth patriarch (五祖) of the Southern Lineage (Nán zōng 南宗) of Daoist nèi dān 內丹 tradition, tracing his initiation through Chén Nǎn 陳楠 back ultimately to Zhāng Bóduān 張伯端. A native of Qióngzhōu 瓊州 (Hǎinán), he became one of the most prolific and culturally important Daoist authors of the Southern Sòng — poet, calligrapher, painter, ritual specialist, and inner-alchemical theorist. His enormous collected works include KR5c0312 Jīn huá chōng bì dān jīng mì zhǐ zhuàn (1225 preface) and its twin KR5c0313 — alchemical scriptures with his commentaries and transmissions. Bái’s dating follows the standard scholarly consensus (Skar, Boltz, Schipper).