Tang Chan master, sobriquet Dàdiān 大顛 (“Great Eccentric”); commonly designated Dàdiānzǔshī 大顛祖師 or Dàdiānhéshàng 大顛和尚. Lifedates 732–824 (DILA A001144); dharma-heir of Shítóu Xīqiān 石頭希遷 (700–790), the founding patriarch of the Shítóu line of Tang Chan. Native of Xǔzhōu 許州 (in modern Hénán). Resident principally at Cháoyáng 潮陽 in Cháozhōu 潮州 prefecture (Lǐngnán, modern Guǎngdōng).
He is best known for his dialogues with the famous Confucian gǔwén writer and anti-Buddhist polemicist Hán Yù 韓愈 (768–824), when Hán was exiled to Cháozhōu in 819 for memorialising against the Tang court’s reception of the Buddha-finger relic (Lùn fógǔ biǎo 論佛骨表). According to the Jǐngdé chuándēng lù 景德傳燈錄 and other Sòng yǔlù compilations, Hán visited Dàdiān, was deeply impressed, and developed a more sympathetic attitude to Buddhism in his later years.
His attested works include the Bōrě xīnjīng zhùjiě 般若心經註解 (X573 = KR6c0192) and the Jīngāng jīng zhùjiě 金剛經註解 (X487). However, both attributions are uncertain — most Tang Chan masters of his stature left only yǔlù (recorded sayings) rather than formal scriptural commentaries, and the doctrinal style of these works (with developed Sòng-period Chan phrases like qīng-qīng cuì-zhú jìn shì zhēnrú “green-green bamboo all is true-suchness”, yù-yù huáng-huā wú-fēi bōrě “lush-lush yellow flowers none not Prajñā”) suggests Sòng or later composition. The works are likely pseudepigraphic Chan-school attributions to Dàdiān, common in the late-Sòng / Yuán / Míng Chan textual culture.
He died Chángqìng 4 (824), age 93. The Cháozhōu jūnzhì 潮州郡志 and other regional gazetteers preserve substantial materials on his Cháozhōu residency and the local cult that grew up around him after death.