Kokaku (date of birth and death unknown) was a priest of the Tendai Sect in the late Heian period. He was a child of FUJIWARA no Mototoshi, a well-known poet. He was a Hokkyo (the third highest rank for Buddhist priests).
He entered Enryaku-ji Temple and studied under Otani zasu Chujin. He called himself Sugiubo Hokkyo due to the fact that he resided in Sugiubo, Higashi-Sakamoto, Omi Province. He was devoted to the study of the Tendai Sect, especially, the Eshin-ryu Branch, and became the founder of a branch called Mudoji-ryu or Sugiu-ryu in his later years. He taught Hangen (rumored to be the biological child of Kokaku) and Koen among others, and authored works such as "Ichidaishinchisho," "Goji Guketsu," "Sanjushikakotogaki," "Sanjujo Kudensho," "Sugiu makurasoshi," and "Honkaisho."
He served FUJIWARA no Tadazane and is said to have also been a religious advisor to him. Winning the full confidence of Tadazane, he is also known to have played a key role in Kuyo (services held for the deceased) at Mi-do Hall of Uji Joraku-in Temple, in Issaikyoe at Uji Byodo-in Temple, and in the funeral of Kayano-in FUJIWARA no Taishi, a daughter of Tadazane.