Ninkaku (1045 - April 17, 1102) was a priest of the Tendai Sect during the latter part of the Heian period. He was the thirty-seventh Tendai-zasu (head priest of the Tendai sect). He is related to Murakami-Genji (Minamoto clan). He was the third son of MINAMOTO no Morofusa who was assigned to Tsuchimikado udaijin (minister of the right). His mother was FUJIWARA no Takako who was the first daughter of FUJIWARA no Michinaga. His brothers and sisters were Sadaijin (minister of the left) MINAMOTO no Toshifusa, udaijin (minister of the right) MINAMOTO no Akifusa, MINAMOTO no Reishi (a wife of FUJIWARA no Morosane) and so on. Dainagon (chief councilor of state) MINAMOTO no Morotada was his younger paternal half-brother. He was given the name Ichijobo as his go (byname).
He learned from Sojo (high-ranking Buddhist priest) Keihan, and was given kanjo (a ceremony to be the successor) from Tendai-zasu Myokai. In 1066 he was assigned to hogen (the second highest rank for Buddhist priests) and was promoted to gon daisozu (Junior prelate) in 1067. In March 1074, he was assigned to the regent of the Byodoin Temple and to hoin (the highest rank among Buddhist priests) in December in the same year, and was transferred to the zasu of the Hossho-ji Temple in 1077. In 1086 he was assigned as gon no sojo (a highest ranking priest, next to a sojo) and in 1091 he was promoted to Sojo (high-ranking Buddhist priest). In 1093 he was assigned to the thirty-seventh Tendai-zasu. In 1095 he was promoted to daisojo (a Buddhist priest of the highest order) and also put in charge of the betto (the superior of a temple) of the Shorenge-in Temple from 1096 and the zasu of the Hojo-ji Temple from 1098 at the same time. In 1100 he held a memorial service for the dead at the Butsugen-in Temple and was assigned to kengyo (temple or shrine administrator). In January 1102 when his sister Reishi became a priestess, he was put in charge of kaishi (the priest who imparts the Buddhist commandments), but he entered nirvana because of a coughing disease at Tsuchimikado-dai residence at the age of fifty-eight on April 24 during the same year. He was buried at the Rendaibe grave in accordance with his will. He showed good performance in the methods of esoteric Buddhism, among which Shijokoho (way of prayer), anchin-ho (an esoteric rite for achieving peace and security of the state or of a new home), Shichibutsu yakushi ho (the method of the Yakushi and other six related wise men used for a long life, health and a safe delivery) and a prayer for curing the disease of Emperor Horikawa were known. At the time of the Ninkaku's death, FUJIWARA no Munetada said that 'he knew well about the mantra and especially efficacious methods in esoteric Buddhism. It is a real pity that he passed away suddenly. Not only the Emperor (Emperor Horikawa) but also all his family are mourning.' (in the section of March 28 in 'Chuyu-ki dairy').
His waka (a traditional Japanese poem of thirty-one syllables) was selected for 'Kinyo wakashu' (Kinyo Collection of Japanese poems) (No.632).