Chéngguān 澄觀 (738–839, longevity 102 suì per the Sòng gāosēng zhuàn 宋高僧傳, T2061), conventionally styled Qīngliáng 清涼 (after his long residence at the Qīngliángsì 清涼寺 on Mt. Wǔtái 五臺山) and posthumously Qīngliáng guóshī 清涼國師 (“National Preceptor of Qīngliáng”), is the fourth patriarch of the Chinese Huáyán 華嚴 school. Native of Shānyīn 山陰 in Kuàijī 會稽 (modern Zhèjiāng), of the Xiàhóu 夏侯 clan. He took ordination at the Bǎolínsì 寶林寺 under Pèi 霈, received the full precepts at the Miàoshànsì 妙善寺 under Chángzhào 常照, and pursued an unusually catholic Buddhist education under teachers from multiple traditions: he studied Tiāntái under 湛然 Zhànrán; Niútóu Chán under Zhōng of Jīngshān 徑山欽 and Wúmíng of Luòyáng 洛陽無明; Northern Chán under Huìyún 慧雲; and the Hézé Southern Chán of 神會 Shénhuì (whose lineage he formally entered, and to which he is conventionally assigned in Tang Buddhist sectarian historiography). His Huáyán education was through DàShēn 大詵 (a sub-disciple of 法藏 Fǎzàng) at the Eastern Capital, supplemented by his early study of Fǎzàng’s Wǔ jiào zhāng 五教章, the Qǐxìn lùn 起信論 commentary tradition, the Fǎjiè guān 法界觀, and Fǎzàng’s Huāyán huányuánjì 還源記.
In Dà-lì 大曆 3 (768) he was summoned to the imperial Dà-fú-sī-sì 大福寺 in Cháng’ān to assist 不空 Amoghavajra as “polishing-prose master” (潤文大德) in his translation team. He subsequently moved to Mt. Wǔtái, residing chiefly at the Dà Huáyán-sì 大華嚴寺 (also known as the Xiǎnxiàng yán 顯象巖 and from his time as the Qīngliáng-sì 清涼寺), where he composed his great commentary on the new (80-fascicle) [[KR6e0010|Huáyán jīng]]. Per the Sòng gāosēng zhuàn and the Lóngxīng biānnián tōnglùn 隆興編年通論, he also collaborated with the Kashmirian Tripiṭaka master Prajñā 般若 in translating the [[KR6e0019|40-fascicle Sì shí Huáyán 四十華嚴]] (T0293) at Cháng’ān in 798.
His principal works are the [[KR6e0011|Dà fāngguǎng fó huáyán jīng shū 大方廣佛華嚴經疏]] (T1735, 60 fasc.); its sub-commentary, the [[KR6e0012|Suí shū yǎn yì chāo 隨疏演義鈔]] (T1736, 90 fasc.); the Sān shèng yuánróng guānmén 三聖圓融觀門 (T1882); the Dà huáyán jīng lüè cè 大華嚴經略策 (T1737, KR6e0015); the Xīn yì huáyán jīng qī chù jiǔ huì sòng shì zhāng 新譯華嚴經七處九會頌釋章 (T1738, KR6e0016); and many shorter doctrinal treatises and ritual texts. Through his disciple 宗密 Zōngmì (780–841) — a major Buddhist syncretist and the fifth Huáyán patriarch — Chéngguān’s doctrinal synthesis became the basis of the entire Huáyán school’s mature curriculum. He served as preceptor to seven Tang emperors (from Dàizōng 代宗 through Wénzōng 文宗) and was awarded the imperial titles Zhènguó dàshī 鎮國大師 (“Great Master Stabiliser of the State”), Dàtǒng guóshī 大統國師, and Dàzhào guóshī 大照國師 in his lifetime. His longevity (102 suì), his activity across nine reigns and seven imperial courts, and his consolidation of the Huáyán doctrinal corpus together make him the central figure of the second generation of Tang Huáyán Buddhism.