The martial arts world has lost a legend ... Toshihiko Koga -- who won a gold medal at the 1992 Barcelona Olympics -- died at 53 years old Wednesday, officials in Japan confirmed.
The judo champ -- a 3-time Olympian -- had reportedly battled cancer in the past year ... though it's unclear if that was the cause of his tragic death.
Japanese politician Katsunobu Kato lamented the loss of Koga at a news conference Wednesday ... telling reporters, "He was so young, and the news of his death is such a shame."
"I express my deepest condolences."
In his first run in the 1988 Seoul Olympics with the Japanese national team ... Koga failed to medal -- but just four years later in Barcelona, he won gold, battling through a leg injury to come out with the hardware.
At the ensuing 1996 Games in Atlanta, he won a silver medal in the -78 kg division.
Koga ended up retiring four years later in 2000 ... and went on to coach the Japanese women's judo team.
He was so successful in that role, one of his students, Ayumi Tanimoto, went on to win a gold medal at the 2004 Games in Athens.