In Judo, how many people have been promoted to 10th dan by the Kōdōkan?

Only fifteen people have been promoted to 10th dan by the Kōdōkan. Twelve were promoted between 1935 and 1984. The other three were promoted together on 8 January 2006, and they are the only living 10th dan-holders recognized by the Kōdōkan.

Other judoka have been promoted to 10th dan by the IJF, though not recognised by the Kōdōkan, which recognises no grades other than its own. Some national (country) associations, continental unions and independent (often multi-style) bodies have also promoted judoka to 10th dan.

Jigorō Kanō (Japan, 1860–1938) founded judo, and established the Kōdōkan in 1882. Judo was the first Japanese martial art to gain widespread international recognition, and the first to become an official Olympic sport. Kanō was also a pioneer of international sports. Accomplishments included being the first Asian member of the International Olympic Committee (IOC). His official honours and decorations included the First Order of Merit and Grand Order of the Rising Sun and the Third Imperial Degree. He was inducted to the IJF Hall of Fame on 14 May 1999. The IJF Hall of Fame was established in 1999. Only three people have ever been inducted into it.