Maris Strombergs of Latvia overcame the threat of a handful of strong, younger challengers to become the Olympics' first repeat BMX champion on Friday.
Australian Sam Willoughby finished second for the silver with Carlos Oquendo of Colombia taking the bronze.
Strombergs, 25, claimed the maiden Olympic men's BMX gold when the sport made its debut in Beijing four years ago.
And despite coming up against younger riders who had shown their mettle in the unforgiving quarter-final and semi-final races, the Latvian stepped up when it mattered most.
He shot off the eight-metre high ramp and quickly built a slight lead on the rest of the eight-man field.
Willoughby, 20, was hot on his heels but with several jumps and berms to negotiate, neither rider was free of danger.
British gold medal hope Liam Phillips came down on the penultimate berm and struggled to rejoin the field after he could not clip his foot back on to his pedal.
It left the hosts without a medal as only minutes earlier Shanaze Reade could only finish sixth in the women's final.
Despite Willoughby's attempt at a late fightback on the closing bumps, Strombergs held on to triumph.
Before the competition, the Latvian had expressed his doubts in the face of strong competition.
After winning gold, he said: "It's so tiring and I still can't believe it. Deep inside I was confident but I think my nerves got the best of me, especially at the beginning of the race yesterday and today.
"But I tried to keep calm and I had a good conversation with my coach before the last moto (race) and deep inside I was confident.
"It's amazing. I still can't believe it. I need a few more minutes, man. It's just amazing."