In the final he came from behind to beat fellow Australian Joel Parkinson: needing a 9.1 on his final wave with four minutes left on the clock, the twice world champion produced a 9.5.
He had waited out his friend Parkinson, who failed to score on the wave previous to Fanning's clincher.
Fanning's trophy cabinet now only lacks The Pipeline Masters in Hawaii among the major events.
At the halfway point of the 10-event season, Parkinson leapfrogs 11-times world champion Kelly Slater, the defending champion who dropped out in round three.
"It's a 35-minute heat, I knew I had time. I just kept my patience. It's the final, you've got nothing to lose and everything to gain," Fanning, 31, said.
"You've got to sit there and it can turn on and off so quick here and you can get two scores pretty quick.
"I didn't have priority that first one I made Joel go... and then the last one I was so stoked to come out.
"I had to do a lot of hard work and to hold on I'm just super stoked."
Parkinson, who is yet to win in Tahiti, said his final wave choice cost him.
"I led a 35-minute heat until four minutes to go, just one bad wave choice," he said.
"You can't really dispute that, he was one of the best surfers for the whole event but it hurts for sure.
"It keeps me coming back... but it just would have been so sweet to have that Teahupo'o trophy, but at least I'm back next year and I'll fight for it again."
1 18.87 Mick Fanning AUS
2 18.37 Joel Parkinson AUS
1 18.93 Mick Fanning AUS
2 18.10 Owen Wright AUS
1 17.14 Joel Parkinson AUS
2 15.17 John John Florence HAW
1 19.07 Mick Fanning AUS
2 18.64 Ricardo Dos Santos BRA
2 15.60 CJ Hobgood USA
1 18.90 Owen Wright AUS
1 16.50 Joel Parkinson AUS
2 16.43 Jeremy Flores FRA
2 4.17 Gabriel Medina BRA
1 16.17 John John Florence HAW