Hōzōin In'ei (宝蔵院 胤栄?, 1521 – October 16, 1607) was a Buddhist monk, head of the Hōzōin temple, and guardian of all the temples of Nara, who founded a school of Sōjutsu called Hōzōin-ryū. In'ei was a connoisseur of the martial arts, having practiced Nen-ryū under Toda Yosaemon and Iizasa Chōisai Ienao's Katori Shinto-ryū. In'ei was noted for having arranged the meeting between Kamiizumi Ise no kami Nobutsuna and Yagyū Sekishusai Muneyoshi, being the catalyst for the creation of Yagyū Shinkage-ryū.
He passed on leadership of the school to other Buddhist monks of his order, including Hōzōin Inshun (1589-1648), Hōzōin Insei (1624-1689), Hōzōin Infū (1682-1731), and Hōzōin Inken (1746-1808).
The school was revived and updated in the nineteenth century by Takeda Sōkaku (1858-1943), who introduced the use of bamboo practice swords (shinai).
In'ei and his school feature in the manga series Vagabond, in which he has retired as master of Hōzōin-ryū, only to train Miyamoto Musashi to defeat his successor.