Shinzei 眞濟 (also written 真濟; 800–860) was a senior disciple of Kūkai 空海 (774–835) and the foremost early-Heian Sanskritist of the Japanese Shingon school. Born into the Ki 紀 clan, he entered Kūkai’s circle at Takao-san-ji 高雄山寺 (later Jingo-ji 神護寺) in his youth and became its first abbot after Kūkai’s death; the temple eventually came to be associated with the Takao-ryū transmission line of Shingon ritual. In 836 he was selected as one of the candidates for Ennin’s 圓仁 mission to Tang China, but the embassy was disrupted by storms and he never reached the continent.
Shinzei is principally remembered for two scholarly achievements: (1) compiling the Shōryōshū 性靈集 (Henjō hokki shōryōshū 遍照發揮性靈集), the collected literary writings of Kūkai in ten fascicles, with prefaces and annotations — the canonical edition of Kūkai’s secular and ceremonial prose; and (2) preserving, through his Takao-san-ji kuden KR6t0172 and the companion Five-family heart-record KR6t0173, a major portion of the oral teaching Kūkai delivered at the Takao centre in the 820s.
In Shingon scholastic genealogy, Shinzei stands as the parallel-and-counterpart to Jitsue 實慧 (786–847): where Jitsue specialised in the practical ritual lineage (Hinoki-no-o / Kōyasan), Shinzei specialised in the doctrinal-philological lineage (Takao / Jingo-ji). After Kūkai’s death he was successively daihōshi and abbot of Jingo-ji; he died in 860 at the age of 61.
Surviving works in the Kanripo corpus: KR6t0172 Takao kuden (1 fasc.); KR6t0173 Five-family heart-record (1 fasc.).