The team of Tianna Madison, Allyson Felix, Bianca Knight and Carmelita Jeter raced away from their closest challengers Jamaica to take gold in a time of 40.82.
Felix said: 'It's an honour to be part of this team. Who would have thought that we would have had a world record tonight? It's amazing. Our names are going down in history.'
The Jamaicans ran a national record of 41.41, but still finished well adrift, while Ukraine took the bronze.
Asli Cakir Alptekin took gold in a scrappy 1500m. The Turkish athlete won a slow race in 4:10.23, finishing ahead of compatriot Gamze Bulut, with Bahrain's Maryam Yusuf Jamal third.
Ethiopian Meseret Defar claimed gold in the women's 5000m.
Defar denied her compatriot Tirunesh Dibaba the chance to add another title to the 10,000m crown she won a week ago. Dibaba also won gold in both events at Beijing 2008.
Kenya's Vivian Cheruiyot was second with Dibaba getting the bronze.
Bahamas won the men's 4 x 400m Relay final in 2:56.72, with the USA second and Trinidad third, 0.31 ahead of Great Britain.
South Africa, with Oscar Pistorius running fourth, finished in eighth place.
Russia's Tatyana Lysenko won the women's Hammer Throw in an Olympic record of 78.18m while France's Renaud Lavillenie took the men's Pole Vault crown.
Australia and New Zealand enjoyed a golden day on the water at Weymouth and Portland in the Sailing.
Mathew Belcher and Malcolm Page finished first for the green and gold in the men's 470 class and were followed to the top of the podium by Jo Aleh and Olivia Powrie of New Zealand in the women's equivalent.
Tunisia's Oussama Mellouli won the men's 10km Marathon open water Swimming and then hinted at retirement.
Mellouli, who won the bronze in the 1500m Freestyle in the pool last week, finished the race ahead of Germany's Thomas Lurz and Richard Weinberger of Canada.
Mellouli said: 'I can't explain it, I can't really describe it.
'I don't think this has ever been done before. This is probably one of the toughest things to do.'
As for his future, he added: 'There's no way I can top this achievement.
'Today I became the first to get medals in the pool and open water. There's no better way than this to leave it all behind me and just enjoy life.'
Champions the Netherlands successfully defended their title to spoil Argentina captain Luciana Aymar's farewell to international Hockey on her 35th birthday.
Olympic gold is the only medal the South American playmaker and seven-time world player of the year has not won and she admitted victory in the final would give her 'eternal glory'.
However, arguably the greatest player in the history of the women's game bowed out having won two silvers and two bronzes in her four Olympic appearances.
A cagey game was settled midway through the second half as the world number ones scored two penalty-corner goals in relatively quick succession from Carlien Dirkse van den Heuvel and captain Maartje Paumen.
Reigning Olympic Synchronised Swimming champions Russia held onto their title, winning gold in the Team event.
The squad won out with a combined score of 197.030 for their Technical and Free routines, both set to music by Denis Garnizov.
China were beaten into second place, with a combined score of 194.010, while Spain clinched bronze with 193.12.
Mariana Pajon won the women's BMX Racing - Colombia's second-ever gold medal - after profiting from a fast start with Maris Strombergs winning the men's equivalent.
Russia are one win away from a fourth Olympic Volleyball title after emerging 3-1 winners from an all-European semi-final with Bulgaria. They will play Brazil, who coasted past Italy 3-0.
Croatia's men's Water Polo side also edged towards gold after winning their last-four clash with Montenegro 7-5.
They will play Italy for gold after they stunned pre-tournament favourites Serbia 9-7.
Russia claimed their fourth Wrestling gold of London 2012 after Dzhamal Otarsultanov beat Vladimer Khinchegashvili in the 55kg Freestyle final.
Otarsultanov, 25, had never wrestled in a senior World Championships before he came to London, but he performed well at the ExCeL, edging past his 21-year-old Georgian opponent 1-0 4-3.
Jordan Burroughs walked away with gold after becoming the USA's' first Olympic Wrestling champion of London 2012.
USA has a long history of successful Olympic Wrestling campaigns, but they had not won gold in London until Burroughs defeated Iran's Sadegh Goudarzi 1-0 1-0 in the 74kg Freestyle event.
France remain on course to become the first team ever to defend their Olympic title in the men's Handball competition after a 25-22 semi-final victory over Croatia.
They will meet Sweden in the title match following the Scandinavians' 27-26 win over Hungary.
The USA and Spain set up a showpiece final in the men's Basketball.
Spain rallied behind 16 points from Pau Gasol to beat Russia 67-59 while the USA proved too strong for Argentina, winning 109-83.
Sebastian Eduardo Crismanich of Argentina won gold in the -80kg Taekwondo division, beating Nicolas Garcia Hemme of Spain 1-0 in the final.
Hwang Kyung Seon of Republic of Korea took gold in the women's -67kg Taekwondo.