Teishun 貞舜 (also read Jōshun, c. 1334–1422; orthography varies as 禎舜 in the CANWWW record), was a medieval Tendai master of Hiei-zan associated with the Kashiwabara 柏原 lineage — one of the principal sub-lineages of the Sammon-school Tendai. He flourished in the late Nanboku-chō and early Muromachi periods.
His principal surviving doctrinal work is KR6t0072 Zōngyào Bǎiyuán ànlì (the six-fascicle Doctrinal Essentials in the Kashiwabara Lineage’s Established Positions) — a comprehensive scholastic-debate compendium of the disputed doctrinal positions of the Kashiwabara line, organized as a series of catechetic ànlì (established positions) covering the trikāya, the Lotus’s “manifestation-of-the-prior” doctrine, the yuánjiào hongaku theology, the Sannō honji-suijaku tradition, and the yuánmì esoteric-exoteric synthesis.
The work is one of the most comprehensive surviving witnesses of medieval Tendai scholastic-debate culture, and remained an authoritative reference for the Kashiwabara lineage through the Edo period.
Within the Kanripo corpus his preserved work is KR6t0072 Zōngyào Bǎiyuán ànlì.
No CBDB record (Japan-only figure). No DILA Authority record currently locates him by certain identification.