Ryuzen (1038 - August 21, 1100) was a Hosso sect Buddhist monk in the late Heian period. His father was FUJIWARA no Masakane, the Sashosho (Minor Captain of the Left Division of Inner Palace Guards), or according to an opinion, MINAMOTO no Masakane.
He studied the doctrines of Yuishiki, Inmyo, and Hosso under Enen sozu of the South hall of Kofukuji Temple. In 1073, he served as an instructor in a Buddhist service Yuimae, was appointed an administrative position Risshi in 1082, served as the chief priest and the highest ranked monk Hoin at Kofukuji Temple, and was appointed a high-ranked administrative position Gondaisozu. In 1087, he founded Daijoin Temple in Kofukuji Temple to become the first head priest, and laid a foundation for Daijoin Temple as a monzeki temple (a temple of high rank where members of imperial family and nobility enter the priesthood), which was comparable to Ichijoji Temple. In 1096, he was appointed gon no betto (acting chief) of Kofukuji Temple and concurrently served as an official of Hasadera Temple and Daianji Temple in Yamato Province.