The Ki Society (気の研究会, Ki no Kenkyūkai) is an aikido organization founded by Koichi Tohei in 1971, while he was the chief instructor at the Aikikai Hombu Dojo. The official Japanese name of the organization is Shin Shin Toitsu Aikido Kai (心身統一合気道会), but it is also known in English-speaking countries as "Ki Society". Its foundation reflected Tohei's differences with the Aikikai, and his own emphasis on developing the concept of Ki. Students of the art are graded in Ki and Aikido classes. Tohei's Ki lessons come from Shin Shin Tōitsu-dō (心身統一道), meaning "the way of realizing the [original] unity of mind and body". The martial discipline of the art is frequently referred to as Ki-Aikido, particularly in the Western world.
The Ki Society has its organizational headquarters in Chiyoda-ku in central Tokyo, and its head dojo at the Tenshinkan in Tochigi Prefecture, a large facility built on the Tohei family ancestral land.