Gesshū Sōko 月舟宗胡 (Genna 4 → 1618; Genroku 9 / 1696), Edo-period Japanese Sōtō-Zen master, principal teacher of 道白 Manzan Dōhaku (1636–1715) and one of the senior figures of the late-17th-century Sōtō fukko movement. Style-name (字) Gesshū 月舟 (“Moon-Boat”); dharma-name Sōko 宗胡.
Successively abbot of:
- Daijō-ji 大乘寺 in Kaga 加賀 (the Tettsū Gikai-line foundation, where he was abbot in his middle career);
- and Kasshōrin / Kasshōji-rin 葛聖林 in Echizen (his late retreat-monastery).
Gesshū was a leading figure of the late-Edo Sōtō scholastic revival. Among his significant doctrinal compositions:
- A revised commentary on Dōgen’s KR6t0286 Fukan zazen-gi.
- Commentaries on the Cáodòng-school Five Ranks (Shōhen goi 正偏五位).
- His own recorded sayings, the Gesshū oshō i-roku 月舟和尚遺録 (KR6t0302), preserved by his disciple Sōgen 曹源 and printed posthumously in Genroku 12 / 1699 with a preface by his heir 道白 Manzan Dōhaku.
Manzan’s preface to the i-roku identifies Gesshū as the principal source of his own fukko doctrine — particularly the principle of menju 面授 (face-to-face transmission) and eshi 嗣書 (succession-letter) authentication that became the central institutional reform principle of the Sōtō Mansan-ha 卍山派 in the early 18th century.