Shinjaku Shinnō 真寂親王 (886–927), born Saneyo Shinnō 齊世親王, was the seventh son of Emperor Uda 宇多天皇 (867–931) and an early imperial-prince-monk (hosshin’ō 法親王) of the Heian Shingon school. He took ordination at Ninnaji 仁和寺 — the great imperial monastery founded by his father — under his father’s preceptor Yakushin 益信 (827–906), the founder of the Hirosawa-ryū 廣澤流 lineage of Shingon. He rose to the rank of hosshin’ō and held senior monastic appointments throughout his life.
Shinjaku’s principal scholarly contribution to medieval Shingon was the systematic transcription into writing of the oral teachings that had descended from Jitsue 實慧 (Kūkai’s senior disciple) through Yakushin. His preserved Bùguàn líng děng jì KR6t0175 (dated 922) is one of the earliest extant documents of early-Heian imperial-house esoteric practice — including notes on the non-pour anointing bell procedure, the wrathful-king mudrās, and the Acala summoning-rite. He stands as the documentary lynchpin between Kūkai’s first-generation oral teachings and the systematic ritual literature of the Hirosawa branch.
Surviving work in the Kanripo corpus: KR6t0175 Bùguàn líng děng jì (1 fasc., 922 CE).