Ninjitsu (1091-July 11, 1131) was a priest of the Tendai sect in the late Heian period. As the second son of FUJIWARA no Kinzane, his mother was FUJIWARA no Koshi (a daughter of FUJIWARA no Takakata) and he was an older paternal half-brother to Taikenmonin FUJIWARA no Shoshi.
Ninjitsu entered the temple on Mt. Hiei and learned about the Tendai Sect while studying under Ninkaku, Ningen, Keicho, Ningo, Shokaku and Sokan. As a Gojiso (a priest who prays to guard the Emperor), he served Tobain and Sutokuin. In 1123, assuming the post of Tendai-zasu (the head priest of the Tendai sect) at the youthful age of 33, Ninjitsu was the first case of anyone assuming the post younger than the age of 40. Filling the post of Kanjo Daiajari (a priest who has received the special anointment transmitting the teaching and rituals of esoteric Buddhism) of Saisho-ji Temple and Sonsho-ji Temple, Ninjitsu retired from his post as Tendai-zasu in 1131. Later on, Ninjitsu became the Shobodai-in betto (the head priest of Shobodai-in Temple) and Hosho-ji Gon no betto (acting head priest of Hosho-ji Temple), but died on July 11th, 1131.