The Hawaiian 19-year-old beat Australian veteran Joel Parkinson in the final to win his first ever ASP World Championship Tour event in his rookie season.
"This is the best feeling in the world," Florence said.
"I had that bad heat at Arpoador to start and we had a couple of lay days and I had to just sit and think about it. I can't even believe this right now. I'm in shock. I was just sticking to my game plan and not thinking about the other guys. I'm so happy right now."
Florence, who now sits at number six on the ASP WCT, will look to carry the momentum from the massive victory to the upcoming ASP WCT events in Fiji and Tahiti.
"This helps my confidence so much," Florence said.
Parkinson was left disappointed after never really getting into the final.
"It's a good feeling I suppose," Parkinson said. "It's a long way to go and I don't want to get too far ahead of myself, but I'm stoked.
"I've had a couple of really nice consistent results. I have been in this position before though so I'm hoping to maintain my performance level throughout the rest of the year."
BILLABONG RIO PRO FINAL:
1 - John John Florence (HAW) 16.37
2 - Joel Parkinson (AUS) 11.44
BILLABONG RIO PRO SEMIFINALS RESULTS:
SF 1: Joel Parkinson (AUS) 15.83 def. Mick Fanning (AUS) 15.00
SF 2: John John Florence (HAW) 17.94 def. Josh Kerr (AUS) 11.86
BILLABONG RIO PRO QUARTERFINAL RESULTS:
QF 1: Joel Parkinson (AUS) 13.90 def. Tiago Pires (PRT) 12.60
QF 2: Mick Fanning (AUS) 16.57 def. Alejo Muniz (BRA) 5.90
QF 3: John John Florence (HAW) 14.94 def. Julian Wilson (AUS) 9.43
QF 4: Josh Kerr (AUS) 15.84 def. Adriano de Souza (BRA) 14.27