Yīshān Yīníng 一山一寧 (Jp. Issan Ichinei, 1247–1317) — Late-Sòng / early-Yuán Chinese Línjì-school Chán master who emigrated to Japan in 1299 as the Yuán-court envoy and remained as a Zen master. Posthumous Japanese imperial title Issan Kokushi 一山國師 / Myōji Kōzai Kokushi 妙慈弘濟國師 (“National Master Wonderful-Compassion Widely-Saving”).
Born Chúnyòu 7 (1247) in Tāizhōu 台州 (modern Línhǎi, Zhèjiāng). Studied at Tiāntái Mountain and received Línjì-school transmission. Dispatched to Japan by the Yuán Chéngzōng 元成宗 emperor in 1299 in connection with the post-invasion diplomatic effort; initially detained as a suspected spy by Hōjō Sadatoki 北條貞時, but soon recognized as a genuine Zen master and welcomed at Kenchō-ji 建長寺. Subsequently became second abbot of Engaku-ji 圓覺寺, abbot of Jōchi-ji 淨智寺 in Kamakura, and in 1313 — at imperial invitation — third abbot of Nanzen-ji 南禪寺 in Kyoto.
Beyond his Zen teaching, Yīshān was a major catalyst of Gozan literature 五山文學 — the Chinese-style literary culture of the Japanese Zen monasteries that flowered in the Muromachi period. His pupils in Chinese letters included future Gozan literary patriarchs.
Died at Nanzen-ji between 1317 March 24 and 1318 February 9 (per DILA estimation). His Recorded Sayings — Issan Kokushi goroku 一山國師語錄 (KR6t0259, T80n2553) — two fascicles, were compiled by his disciples Ryōshin 了真 and others.
Source: standard Japanese Rinzai-Zen biographical sources; Pollack, David, The Fracture of Meaning: Japan’s Synthesis of China from the Eighth Through the Eighteenth Centuries, Princeton: Princeton University Press, 1986 (on Gozan literature); Collcutt, Martin, Five Mountains (1981).