LONDON - Five things to know about Saturday, Day 8 of the London Olympics:
-One last splash: Phelps grabs 22nd medal with U.S. medley relay win.
-Britannia you rock! An Olympic day to remember for the hosts.
Members of the United States team Matthew Grevers, left, Michael Phelps, middle and Brendan Hansen celebrates as Nathan Adrian finishes in the men’s 4 X 100-meter medley relay.
-Pistorius makes 400 semis in Olympic debut.
-LeBron and Co. pushed in U.S. hoops win over Lithuania.
-Serena Williams gets a Golden Slam, beats Sharapova in tennis final.
When it was over, Michael Phelps hugged his teammates, then headed off the deck for the final time.
Reclaiming the lead with his trademark butterfly stroke, Phelps won the 18th gold of an unparalleled career when he helped the U.S. win the 4x100-meter medley relay Saturday night.
Phelps retires with twice as many golds as any other Olympian, and his total of 22 medals is easily the best mark, too.
"It's been a great career," he said. "It's been a great journey. I can't be any more happy than I am."
The U.S. women also won the medley relay on swimming's final night at the games, setting a world record in the final. Ranomi Kromowidjojo of the Netherlands took the women's 50-meter freestyle to complete a sweep of the sprints, and China's Sun Yang lowered his own world record while winning the men's 1,500 freestyle.
Britain's banner day stretched from Dorney Lake to Olympic Stadium, which opened with Oscar Pistorius' debut and ended with a crowd-pleasing performance by the home team.
How to describe the action in track and field? The Blade Runner and Britannia.
Pistorius, a double-amputee who runs on carbon-fiber blades, finished second in his 400-meter heat to earn a berth in the semifinals Sunday night. He posted a season-best time of 45.44 seconds.
"I've worked for six years ... to get my chance," said the South African, who became the first amputee to compete on the track at an Olympics. "I found myself smiling in the starting block. Which is very rare in the 400 meters."
Team GB sent a charge through the capacity crowd with a quick series of victories, producing repeated roars that could be heard throughout Olympic Park.
The victors: Jessica Ennis in heptathlon; Greg Rutherford in men's long jump; and Mo Farah in the men's 10,000 meters. Three gold medals in about one hour for the host country - and the capper to a big British surge.
The hosts pulled in two more golds on the final day of the Olympic regatta, and another in women's pursuit at the London Velodrome.
The U.S. men's basketball team was pushed - and then some.
Two days after running and gunning to a record-shattering 83-point win, the United States needed a strong finish from LeBron James to eke out a 99-94 victory over Lithuania.
The Americans trailed 84-82 with 5:50 to play, but James scored nine of his 20 points in the final four minutes to help the U.S. remain unbeaten.
"You want to get tested. The best teams want to be tested. We love the competition," James said. "I think we've got some of the greatest competitors in our league, in this world, so you want to have a game where you feel like you were tested, and we had that today."
Carmelo Anthony also had 20 points for the U.S. (4-0), which looked nearly invincible in thrashing Nigeria 156-73 on Thursday night and breaking several records.
Linas Kleiza scored 25 for Lithuania, which shot 58 percent and outrebounded the U.S. 42-37.
There was no such test for Serena Williams, who blew away the field at Wimbledon.
The American star became only the second woman to achieve a Golden Slam, routing Maria Sharapova 6-0, 6-1 in the most lopsided women's final in Olympic history.
The victory completed a remarkable run of domination by the No. 4-seeded Williams, who lost only 17 games in six matches en route to her first singles gold medal. She went 13-0 this summer at the All England Club, where she won her fifth Wimbledon title a month ago.
"I was so focused here," she said. "I remember I was serving and I was thinking: 'Serena, this is your best chance to win a gold medal. You're at Wimbledon, you're on grass, you play great on grass, pull it together, just win this.' And that's what I thought about."
Top-seeded Bob and Mike Bryan also won Olympic gold for the U.S., beating Michael Llodra and Jo-Wilfried Tsonga of France 6-4, 7-6 (2) in the men's doubles final.
Roger Federer will try to complete a career Golden Slam when he plays Andy Murray of Britain in the men's final Sunday.
The rest of the Olympic action Saturday:
Two-time gold medalists Kerri Walsh Jennings and Misty May-Treanor beat the Netherlands in straight sets to advance to the tournament quarterfinals.
The Americans beat Marleen van Iersel and Sanne Keizer 21-13, 21-12.
Reigning world champions Emanuel and Alison topped Germany 21-16, 21-14 to advance to the men's quarters. The Brazilians, the top-seeded team at the London Games, eliminated Jonathan Erdmann and Kay Matysik.
Nicola Spirig of Switzerland won the gold medal in a photo finish with a Swedish challenger at the Olympic triathlon. The end of the race was so close that both women celebrated after crossing the line.
Spirig held off Lisa Norden to claim gold in 1 hour, 59.48 seconds. The runners were given the same time, and Spirig was declared the winner after a few minutes of uncertainty.
Erin Densham of Australia took bronze on the course through Hyde Park in central London in 1:59.50.
Thousands of spectators lined the route. Fans do not need tickets to watch triathlon events at the London Games.
The U.S. men's team blew a two-set lead and lost to Russia in five, snapping an 11-match winning streak in Olympic play.
Maxim Mikhaylov scored 27 points for No. 2 Russia in the 27-29, 19-25, 26-24, 25-16, 15-8 victory. Sergey Tetyukhin spiked for match point.
Germany, Poland, Argentina and Italy also won.
The British boxing team is on a remarkable roll at its home Olympics, and that's just one reason the Indian team is furious.
Second-seeded light welterweight Tom Stalker beat India's Manoj Kumar 20-16 for the 10th British win in 11 fights in London, moving six boxers to the brink of medal qualification.
Although Stalker and Kumar appeared to be evenly matched, Kumar and his coaching staff criticized the judges and the tournament after the fifth loss for a seven-man team that arrived in London hoping to add to its single Olympic boxing medal.
India did get a nice fight from light flyweight Devendro Laishram, who posted a 16-11 upset of fourth-seeded Serdamba Purevdorj of Mongolia.
Cuba's Roniel Iglesias upset top-seeded Brazilian light welterweight Everton Dos Santos, while top-seeded light heavyweight Julio La Cruz of Cuba overwhelmed Jordan's Ihab Almatbouli.
American Jamie Lynn Gray won the gold medal in women's 50-meter three-position rifle shooting, setting two Olympic records along the way.
Gray clinched gold on her final shot with a 10.8 - just 0.1 off a perfect score.
Ivana Maksimovic of Serbia won the silver, and Adela Sykorova of the Czech Republic was third.
Italy's Jessica Rossi won the gold medal in women's trap shooting, missing just one of 100 shots to set a world record. Her lone miss came on the 18th shot of the 25-shot final.
Zuzana Stefecekova eventually won the silver in a shoot-off, topping Delphine Reau of France.