Tendai-zasu (head priest of the Tendai sect) is a post that serves as the resident priest of Enryaku-ji Temple on Mt. Hiei, the head temple of the Tendai sect, exercising general supervision over all of its sub-temples.
Tendai-zasu was also referred to as the 'Head Priest of the Mountain.'
The Tendai-zasu, however, rarely lived at Mt. Hiei and many of them went to that mountain only on occasions when important services and ceremonies were held.
In 824, Gishin was referred to as Tendai-zasu for the first time. Up to the time of the second head priest Encho, the term Tendai-zasu was a private title used within the compound of Enryaku-ji Temple but, starting with the third head priest Ennin, it became an official post appointed by way of kanpu (official documents from the Dajokan or Grand Council of State) issued by the Dajokan, and which continued until 1871. There have been numerous occasions when the same person received the appointment more than once, with, for example, Jien and Cloistered Imperial Prince Sonen assuming the post of Tendai-zasu 3 and 4 times respectively.
In the early Middle Ages, with the Sekke-monzeki (temples headed by regents) and miya-monzeki (temples headed by imperial princes) systems being in place, cloistered imperial princes from Myoho-in Temple, Joren-in Temple and Sanzen-in Temple (the Tendai Three Monzeki) in particular began to assume the position of Tendai-zasu frequently. Additionally, during the Muromachi period, the post of Tendai-zasu was filled by members of the Ashikaga Shogun family. There are some examples of Tendai-zasu who subsequently returned to secular life to become Seii taishogun (literally, the great general who subdues barbarians) including Imperial Prince Morinaga (his secular name after leaving the priesthood) and Yoshinori ASHIKAGA (also his secular name after leaving the priesthood).
In the Edo period, the grand temples of the Tendai sect in Togoku (the eastern part of Japan, particularly Kanto region), Rinno-ji Temple on Mt. Nikko in Nikko and Kanei-ji Temple on Mt. Toei (Tenkai was the founder and the first chief priest) in Ueno were built by the Edo bakufu (Japanese feudal government headed by a shogun). Rinno-ji Temple was designated as a temple headed by imperial princes (referred to as Rinnojinomiya or Nikko-monzeki), and it was settled that after 1656 Rinnojinomiya had responsibilities both as the resident priest of Toeizan and Tendai-zasu, being responsible for general supervision of the three temples of the Tendai sect above (.Sanzan Kanryo no miya).
In 1871 the designation of the Tendai-zasu was repealed by the Dajokan (Grand Council of State) and the position of Tendai-zasu disappeared, but following the many calls for its restoration both from within the Tendai sect and without, in 1885 it was revived in the form of a private title. Kojun HANDA is the current and the 256th Tendai-zasu. Various records including the appointment log of the successive zasu, services, events and incidents are documented in 'Tendai-zasu ki' (Archives of Tendai-zasu).