Saeki Jōin 佐伯定胤 (Sino-Japanese reading: Zuǒbó Dìngyìn; 1867–1952) was a prominent Hossō 法相 (Yogācāra / Faxiang) master and Buddhist scholar of the late Meiji, Taishō, and early Shōwa eras in Japan. He served as abbot of Hōryū-ji 法隆寺 and was one of the chief figures in the modern Hossō revival, lecturing extensively on 玄奘-school doctrine and editing biographical source-material on the patriarchs of the Chinese and Japanese Hossō tradition.
He co-edited with 中野達慧 (Nakano Tatsue) the Xuánzàng sānzàng shīzī zhuàn cóngshū (KR6r0048), a collected biographical compendium on Xuánzàng and his disciples preserved in the Manji Xuzangjing.