The 21-year-old Wallace, who trained with multiple Olympic gold medal winner Ryan Lochte during his swimming scholarship at the University of Florida, burst through with 50 metres remaining.
Australia's Thomas Fraser-Holmes took silver with Sebastien Rousseau of South Africa third.
"I have never felt anything like this. I wasn't going to waste this opportunity," said Wallace, who echoed his namesake William Wallace in the film 'Braveheart' and screamed "freedom" after touching first, before smashing the water with both arms in delight.
"The Games really have brought out the Scottish side of me so I thought I’d soak up the moment," he told reporters.
"At 200 metres to go, without a doubt, I had the best breaststroke leg in that field.
"Confidence is key. If I didn't wake up thinking I could do it, it would not be worth it."
England’s Ben Proud kick-started the session with a surprise victory in the 50 metres butterfly before Chris Walker-Hebborn ensured England enjoyed double success when he won the 100 metres backstroke in a Games record time of 53.12 seconds.
"I am beyond excited. Tears almost came into my eyes," Proud, who beat South African duo Roland Schoeman and Chad Le Clos in a time of 22.93 seconds, told the BBC.
Australia also enjoyed a successful night in the pool with Fraser-Holmes beating compatriot Cameron McEvoy in a nip-and-tuck 200 metres freestyle race, while Leiston Pickett successfully defended the 50 metres breaststroke title she won in Delhi four years ago.
Canada’s Katerine Savard broke a Games record in the women's 100 metres butterfly before Australia finished off proceedings with gold in the 4 x 100m freestyle relay thanks to Tommaso D’Orsogna, Matt Abood, James Magnussen and McEvoy.
(Reporting by Michael Hann; editing by Toby Davis)
Share
