In 3.5-feet high waves at the left-hand point break of Itauna, in Saquarema near Rio, the 23-year-old sealed his biggest career win and a $40,000 cheque.
Victory also shunts him from number 43 to 17th in the ASP World Ranking.
“I’m so stoked and now I’ve got a hard-on for Brazil,” an excitable Wilkinson said afterwards. “No, I’m just kidding around, but I really am almost crying from all of the emotion.
“I’m really happy with what I was able to accomplish in the semis and the final.
“I had a lot of fun, my board felt really good under my feet and now Saquarema is my favourite place in the world.”
Otton, meanwhile, could not replicate his form in the semis and quarters, failing to complete his first turn after electing to paddle into a wave.
“Everything went wrong for me at the end there,” the 32-year-old admitted. “And to make things worse, Matty (Wilkinson) was doing great all heat long. But congratulations to him, he deserved the victory.”
1. Matt Wilkinson (Australia) 18.43
2. Kai Otton (Australia) 8.63
Otton 13.00 def. Kolohe Andino (USA) 4.67
Wilkinson 17.76 def. Keanu Asing (HAW) 10.67