Junnyū 淳祐 (890–953) — sometimes also read Junyū — was a Japanese Shingon master of the early 10th century, chief disciple of Kangen 観賢 (854–925) of Daigo-ji and ultimately founder of the Ishiyama branch (Ishiyama-ryū 石山流) of medieval Shingon. He held the rank of naiku 內供 (palace chaplain), whence the byname Ishiyama no naiku 石山內供, and resided at the great hall complex of Ishiyama-dera 石山寺 on Lake Biwa, the Kannon pilgrimage centre where Murasaki Shikibu later composed Genji monogatari.
Junnyū’s principal scholarly achievement was the systematization of the iconographic-meditative corpus of Shingon ritual into a sustained dōjō-kan literature — the form he established in his Yàozūn dàochǎng guān KR6t0174 became the template for the wide visualization-manual tradition of medieval Japanese Shingon. He was also reputed as a calligrapher and as a copyist of Tang esoteric ritual texts; the Ishiyama-dera library preserves a number of his autograph fragments.
In Shingon lineage genealogy, Junnyū stands as the bridge between the early-Heian Kangen / Kannin generation and the mid-Heian Ningai 仁海 / Saisen 濟暹 systematic-doctrinal generation; through Ningai (Ono-ryū) and through his own Ishiyama disciples, his transmission diffused into nearly every later branch of Shingon ritual.
Surviving work in the Kanripo corpus: KR6t0174 Yàozūn dàochǎng guān (2 fasc.).