The 24-year-old hit the wall in 51.98sec to edge team-mate Kliment Kolesnikov, who touched in 52.00, ahead of American defending champion Ryan Murphy in 52.19.
Murphy was bidding to make it seven consecutive Olympic gold medals in the event for the United States.
Gold!Evgeny Rylov leads an ROC team one-two in the men’s 100m backstroke.@fina1908 #Swimming https://t.co/YHl50gCp5v
— Olympics (@Olympics) 1627352034000
It is the first time since the Moscow Games in 1980 that an American has failed to win either gold or silver in the 100m backstroke.
Rylov’s superb showing set a new Russian record and he was not far off Murphy’s world record time of 51.85.
He adds an Olympic gold to the bronze he claimed in Rio and two world championship golds in 2017 and 2019, all won in the 200m backstroke.
#Swimming Men’s 100 Backstroke It’s a one-two for Russian Olympic Committee!🥇Evgeny Rylov 51.98 (new European rec… https://t.co/IiN9q1i0Is
— FINA (@fina1908) 1627351616000
Kolesnikov was making his Olympic debut at the Tokyo Aquatic Centre and fully vindicated his placing as the number two seed, with only his compatriot ranked ahead of him.
The 21-year-old, who won bronze at the 2019 world championships in 50m backstroke, is widely considered to be the up and coming star of Russian swimming.
It might have been even better for the youngster after he stormed into an early lead, with Rylov and Murphy in hot pursuit.
Murphy posted the fastest final 50m but had left himself too much to do, with Rylov powering home to secure victory.