Sealing the race by barely more than the ridges on his fingertips, Phelps punched the air and screamed as a capacity crowd in Beijing's stunning Water Cube rose for a standing ovation.

Phelps' gold run

Athens 2004: six gold medals

Beijing 2008:

400m individual medley

4x100m free relay

200m freestyle

200m butterfly

4x200m free relay

200m individual medley

200m butterfly

Serbian officials protested the result, but officials from FINA, swimming's ruling body, reviewed the race and ruled that the results stood.

Victory in the 100m fly brings Phelps his 13th career gold, four more than any other Olympian in history, as well as a not-to-be-sniffed-at $1m bonus from his sponsors.

Phelps previous six golds in Beijing had all set new world record times, and although Saturday's win fell short of that mark it still set a new Olympic record.

Speaking after his seventh stand on the Beijing podium, Phelps admitted he had started to have his own doubts after the halfway point.

"I was starting to hurt for the last 10 metres," he told reporters. "It was my last individual race and I just wanted to finish as strong as I could."

"I feel a little bit of everything - relief, excitement, everything… I had to take my goggles off to make sure the 'one' was next to my name."

With his eyes set on an unprecedented eight golds in a single games, Phelps is now preparing himself for his final race in Sunday’s 100m medley relay.

"I think the biggest thing is when someone says you can't do something," he said of his quest to top Spitz's haul of seven golds at a single games - a record once thought unassailable.

"It shows that anything is possible when you put your mind to it."