Keiji Suzuki defeated Russia's Tamerlan Tmenov by an ippon in the final of the men's over-100kg judo competition to capture the gold medal for Japan.
Suzuki, 24, was making his first appearance on the Olympic stage.
Dutchman Dennis van der Geest produced a superb waza-ari awasete ippon to defeat Iran's Seyed Miran Fashandi and take one of two bronze medals on offer.
Estonia's Indrek Pertelson secured the other bronze after defeating Italy's Paulo Bianchessi by an ippon.
Earlier in the contest, Suzuki had been forced to battle back from a half-point down to floor his Belarus opponent with an ippon with just a minute to go.
His victory could now see Suzuki take over as the icon of Japanese judo from 26-year-old Kosei Inoue, who triumphed in Sydney and has won the world title three times in a row.
But Inoue was upset in the under-100kg quarter-finals on Thursday.