With the victory, Phelps overtook compatriot Mark Spitz, whose seven swimming golds at Munich in 1972 were the most at a single Games.

At 23, and competing in his third Olympics, Phelps took his total of Olympic titles to 14, including six from Athens, where he also claimed two bronze.

The US squad of Aaron Peirsol, Brendan Hansen, Phelps and Jason Lezak won a tight race in 3:29.34, Lezak holding off Australian individual world record-holder Eamon Sullivan on the closing freestyle leg.

The United States were lying third when Phelps hit the water for the penultimate butterfly leg. He had given the United States a narrow lead by the time he handed over to Lezak to finish it off.

The Americans improved on the previous world record of 3:30.68, while Austraila finished second in 3:30.04 and Japan took the bronze in 3:31.18.

Tunisia's Oussama Mellouli ended Grant Hackett's dream of an historic three straight 1500m freestyle golds with a victory in 14:40.84.

Mellouli sprinted clear with 300m remaining and held off the Australian great's spirited finish.

Hackett, the winner of the event in Sydney and Athens and bidding to become the first male swimmer to win three Olympic titles in the same event, took the silver in 14:41.53, only 0.49secs behind.