The Monshu (門主), or keeper of the gate is a term sometimes used in Japanese Buddhism to denote the head of a monastery, as in the case of Jōdo-shū and Tendai Buddhism, but in the case of the Nishi Hongan-ji sub-sect of Jōdo Shinshū Buddhism, it refers to the spiritual leader of the sect, and direct descendant of its founder Shinran.
The Monshu in Jōdo Shinshū Buddhism was the guardian of Shinran's mausoleum, as well as the head of the sect. This position was started when the youngest daughter of Shinran, Kakushinni, installed her son as the custodian of the small shrine which held Shinran's image and ashes at Ōtani, in Kyoto. In time the small shrine grew into what is now the Hongan-ji temples (east and west). When the temple split into two temples, the West Temple, or Nishi Honganji continued to use the term Monshu, while the East Temple, or Higashi Hongan-ji gradually adopted the term "Hossu".
In the line of Monshu descendants, noteworthy Monshu include:
As of writing, the current and 25th Monshu of the Nishi Hongan-ji temple is His Eminence Sennyo Shōnin (Ōtani Kōjun, born 1977). He succeeded his father Sokunyo Shōnin (Ōtani Kōshin, born 1945) on 6 June 2014.