In the women’s event, which took place earlier in the day, Britain’s Beth Potter secured a bronze medal. Minutes after Yee’s win at the Paris Games, Team GB’s women’s quadruple sculls crew claimed gold in a dramatic race to the line.
Britain’s Alex Yee has won gold in the men’s triathlon with a stunning late victory.
The 26-year-old Londoner came into this summer’s Olympics as one of the favourites for his event, along with New Zealand’s Hayden Wilde.
He was more than 10 seconds behind Wilde with around 200 metres to go but produced a phenomenal comeback to earn gold - Team GB’s fifth.
Minutes later, Great Britain’s women’s quadruple sculls crew claimed gold in a dramatic race to the line with the Netherlands.
After a cautious start, Hannah Scott, Lola Anderson, Georgie Brayshaw, and Lauren Henry produced a storming finish in the final 250 metres.
A photo-finish was declared as the two boats crossed the line - but it was the British crew who were punching the air with the margin of victory given as 0.15 seconds.
Scott told the BBC: "It’s been a long time in the making and I still can’t quite believe it. I don’t know if I’m emotional yet but that will come.
"I think we were so process-driven today and the immensity of what this is, it hasn’t caught up with me.
"The crew today were amazing. We kept it so cool to the end. We had the confidence, we’ve done so many hard miles in training and for anyone out there just go for it.
"If you think you can, you might just do it one day, and that’s the really cool thing about the Olympics."
At the last Olympics in Tokyo, Yee walked away from his debut games with two medals and came to Paris as one of the new triathlon stars taking over the mantle from the Brownlee brothers.
Yee went to the ground after completing the race, with second-placed Wilde, sitting down next to him.
Wilde had a 14-second lead going into the final lap of the 10km run.
But Yee - the former British champion over 10,000m - had kept enough in his legs and surged past Wilde in the final stages to cross the finish line first on the Pont Alexandre III.
The run-up to the event had been overshadowed by worries over water quality in the River Seine.
Two training swims were cancelled due to sub-standard water despite Paris having spent €1.4bn (£1.18bn) into making the river ready for the event.
This came after heavy rains on Friday and Saturday in the French capital.
The event was eventually postponed until Wednesday after tests in the early hours of Tuesday morning revealed the water was not clean enough for the race to take place.
In the women’s event, which took place earlier in the day, Team GB’s Beth Potter secured a bronze medal.
She too was tipped for Olympic gold, but ultimately she could not match the pace of home favourite and winner Cassandre Beaugrand, with Switzerland’s Julie Derron finishing second.
"Just relief," said Potter when asked about her emotions. "This day has been in the calendar for a long time and to come away with a medal, I’m just over the moon.
"I just knew that I could tough it out longer than someone else. Gold was in my mind but I just wasn’t good enough today. I’m happy. Gold would have been great but I got a medal."
The women’s race was able to take place as scheduled.