(AP) 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.
-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. Jamaica also got a big victory when Shelly-Ann Fraser-Pryce raced to another gold in the women's 100 meters, keeping the cherished sprinting title in the Caribbean country.
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.