Judo (柔道, jūdō^?, meaning "gentle way") is a modern martial art, combat sport and Olympic sport created in Japan in 1882 by Jigoro Kano. Its most prominent feature is its competitive element, where the object is to either throw or takedown one's opponent to the ground, immobilize or otherwise subdue one's opponent with a grappling maneuver, or force an opponent to submit by joint locking or by executing a strangle hold or choke. Strikes and thrusts by hands and feet as well as weapons defences are a part of judo, but only in pre-arranged forms (kata) and are not allowed in judo competition or free practice (randori).

The philosophy and subsequent pedagogy developed for judo became the model for other modern Japanese martial arts that developed from koryū (古流^?, traditional schools). The worldwide spread of judo has led to the development of a number of offshoots such as Sambo and Brazilian Jiu-Jitsu. Judo practitioners are called judoka.

The early history of judo is inseparable from its founder, Japanese polymath and educator Jigoro Kano (嘉納 治五郎, Kanō Jigorō^?, 1860–1938), born Shinnosuke Kano (嘉納 新之助, Kanō Shinnosuke^?). Kano was born into a relatively affluent family. His father, Jirosaku, was the second son of the head priest of the Shinto Hiyoshi shrine in Shiga Prefecture. He married Sadako Kano, daughter of the owner of Kiku-Masamune sake brewing company and was adopted by the family, changing his name to Kano, and ultimately became an official in the Bakufu government.

Toshihiko Koga (古賀 稔彦, Koga Toshihiko^?, born November 21, 1967) is a retired judoka and Olympic champion who competed in the -71 kg and -78 kg divisions. Koga is regarded as having perhaps the greatist Ippon seoinage ever.

Koga was born in Kitashigeyasu, Saga, Japan. He began judo in elementary school. He traveled to Tokyo during junior-high school to enter Kodogakusha, a judo school later attended by Olympic gold medalists Hidehiko Yoshida and Makoto Takimoto. He continued his education at the Nippon Sport Science University, and captured several awards including five consecutive championships at the Kodokan Cup and six consecutive championships at the All-Japan Judo Championships (all in the 71 kg division). He placed 3rd in the 1987 World Judo Championships held in Essen, and was chosen to participate in the 1988 Summer Olympics, where he lost in the 3rd round of the competition. Koga returned to the Olympics in 1992 after winning the 1989 and 1991 World Judo Championships, but seriously injured his left knee during a randori (sparring) session against Hidehiko Yoshida, which prevented him from using his best technique; the Ippon Seoinage. He won the gold medal overcoming this injury, and was given the JOC Sports Award by the Japanese Olympic Committee.