Huìguǒ 惠果 / 慧果 (746–805) — the seventh patriarch of the Tang Esoteric tradition in the canonical lineage (善無畏 → 一行 → 玄超 → 惠果, and 金剛智 → 不空 → 惠果) and the principal Tang teacher of Kūkai (空海). Native of Wànnián 萬年 (in modern Shaanxi); lay family name Mǎ 馬. Court title Qīnglóng Ācāryā 青龍阿闍梨 (“Ācāryā of the Qīnglóng Monastery”). Born in Kāiyuán 34 = 746 CE; died 9th month of Yǒngzhēn 1 = 805 CE at age 60.
He took early ordination under Tánzhēn 曇貞 at the age of 17, and was soon spotted by Amoghavajra 不空 (不空) who took him as a principal disciple and transmitted the full Vajradhātu Esoteric apparatus. He received full ordination at age 20. He subsequently received the Garbhadhātu and Susiddhi transmissions from Xuánchāo 玄超 (a disciple of Śubhakarasiṃha 善無畏 善無畏) and the Vajradhātu transmission from Amoghavajra. He was thus the first master to formally consolidate the dual-mandala (Garbhadhātu + Vajradhātu) transmission in a single lineage — establishing the Jīn-tāi bú-èr 金胎不二 (“Diamond-Womb non-duality”) doctrine that became foundational for the East Asian Esoteric tradition.
He served as principal master at the Qīnglóngsì 青龍寺 East-Pagoda Cloister in Chángān, the imperial Esoteric monastery. His most consequential single act was the transmission of the dual-mandala to Kūkai in 805, immediately before his own death; Kūkai brought the entire transmission to Japan in 806 and built the Shingon school on its foundation. His other principal disciples included Yìcāo 義操 (義操), who transmitted the lineage to Fǎquán 法全 (法全) and through him to Ennin 圓仁 (圓仁), Enchin 圓珍 (圓珍), and the Japanese Tendai-Esoteric (Taimitsu) tradition.
His extant own composition in the Taishō is the Shíbā qìyìn 十八契印 (KR6j0071, T18n0900) — a brief treatise on the eighteen fundamental mudrās of Esoteric practice — and several attributed ritual manuals.
Source: DILA Buddhist Person Authority A001197; Sòng Gāosēngzhuàn 宋高僧傳 (T50n2061); Dà Tán Shénzhōu Jīnglóngsì gù sānzhāo guóshī Guàndǐng ācāryā xíngzhuàng 大唐神州青龍寺故三朝國師灌頂阿闍梨行狀 (T50n2057, the official Tang biography); Chou Yi-liang, “Tantrism in China”; Ryūichi Abé, The Weaving of Mantra (1999).