The 36-year-old kayaking veteran won the 1,000-meter K-1, holding off a tough challenge from Canada's Adam van Koeverden to cross the finish line in a time of 3 minutes, 26.462 seconds.
And now, he says, he really is retiring for good.
"I am stopping now. This was my last race. It was a really good race," he said. "I'm really happy. I've managed to do what I set out to two years ago. I knew I could do it."
After quitting in 2009, Larsen came out of retirement last year with his sights set on winning back the gold he won at Athens 2004.
And Wednesday's race was one of the hardest races of his life, he said
"The last 100 metres was really tough and I was just happy no one was coming from behind," Larsen said. "I felt good passing the 500 metre mark and then I thought 'OK, this is possible,' and I just had to go harder than I had ever done before and let the crowd push me through the pain."
It was a fitting finish to a distinguished sporting career. Since his international breakthrough in 2000, Larsen had made a considerable mark on the kayaking stage when he made the decision to stop competing, winning Olympic gold in 2004 and a silver in Beijing four years later as well as five World Championship golds.
Comebacks aren't easy for any athlete, especially for so decorated a competitor.
But Larsen was willing to go through challenging times in order to get back to the very top.
"The last two years have been an amazing journey. The first year was really hard. Getting back into training and getting beaten in training every day by guys I didn't want to get beaten by, but I knew I just had to get through it," he said. "This year I have felt things getting more on the right track, especially the last two months after the Europeans and coming into the Olympics."
Luckily for Larsen, his wife Mira knows exactly what he has been going through. She is also an Olympic kayaker and a member of Norway's Olympic team.
"The last two years have been great because we have been travelling together and doing everything together," he said. "I have been able to train as hard as I needed and to stay away from home just focusing on training. Without her on the team I don't think I would be sitting here with the gold today."
Borre Rognlien, president of the Norwegian Olympic Committee, was thrilled with Larsen's success, describing him as "one of the most outstanding athletes Norway has had in summer sports."
"It's not possible to find the right words to describe what I was feeling when he was crossing the finish line. I was standing and screaming with the rest of the Norwegian team," said Rognlien. "I am sure we will ask him (to help with training), I hope he will respond. All the young people in Norway look up to him and he will certainly be asked to do something for Norwegian sport."
But for now, the Norwegian champion will take some time off while he considers his next move.
"I've set everything on hold and I will decide during the fall," he explained. "Now I will just relax, do some hunting, have some vacation."