Gyokko-ryū (玉虎流) is a school of Japanese martial arts that specialises in kosshijutsu (骨指術), shitōjutsu (指頭術) and ninpō (忍法). Gyokko-ryū was founded by Tozawa Hakuunsai Hogen (戸沢白雲斎, 1156-1159) in the Heian period (794–1192). The sōke title was claimed to be passed down to Masaaki Hatsumi (1931-) from Toshitsugu Takamatsu (1889-1972).
- Watatani Kiyoshi, Yamada Tadashi (1978). Bugei Ryuha Daijiten (武芸流派大事典) (Large Encyclopedia of Martial Arts) (in Japanese). Shin Jinbutsu Ourai Sha (人物往来社). p. 229-230.