Shén Kǎi 神愷 was a Tang-period Chinese monk active at the Jiāxiángsì 嘉祥寺 (the Jiāxiáng monastery, traditionally identified with the famous Sanlun-school monastery in Kuàijī 會稽). He is known solely as the recorder (記) of the Dàhēitiānshén fǎ 大黑天神法 (KR6j0518, T21n1287) — a one-fascicle ritual manual for the Esoteric deity Mahākāla (大黑天神), preserved in the Taishō. The colophon styles the work “[Recorded] at Jiāxiángsì by Shén Kǎi” (嘉祥寺神愷記).
According to later Japanese transmission notes (preserved in Shingon-school commentary on the Mahākāla cult), Shén Kǎi was a disciple of Shéntài 神泰, a mid-Tang Faxiang-school exegete and translation-bureau participant under Xuánzàng 玄奘 and his successors. The DILA Buddhist Person Authority (A000989) registers him as a Tang-dynasty monk known only from this single work. The text itself is the earliest detailed Chinese Esoteric manual on Mahākāla and is the foundational source for the East Asian Mahākāla / Daikokuten 大黒天 cult, especially as transmitted to Japan, where it became enormously consequential.
No biography is preserved in the Sòng Gāosēngzhuàn or in the standard catalogues. The dating bracket for his activity is conventionally placed in the mid-to-late Tang on the basis of the linguistic and ritual character of the text (post-Bù-kōng Tángmì redaction).
DILA Buddhist Person Authority A000989.