Ryunosuke Haga (羽賀 龍之介, Haga Ryunosuke, born 28 April 1991) is a male Japanese retired[1] judoka and 2015 world champion in the under 100 kg division.

[2] Born in Miyazaki, Haga started judo at the age of 5.

[2] He won the gold medal in the ‍–‍100 kg weight class at the 2010 World Juniors Championships in Agadir.

[2] In 2015, he won the gold medal in the Half-heavyweight (100 kg) division at the 2015 World Championships.

[7] Furthermore, he maintains a decade-long friendship with Ōzeki Kirishima Tetsuo, a professional sumo wrestler.