ATHENS, Greece - In a rousing start to the much-anticipated Olympic swim meet Saturday, Ian Thorpe won his second straight gold in the 400 freestyle — a race he got into only through the generosity of an Australian teammate — and Jenny Thompson was denied her recordtying ninth gold medal when she gave up the lead to Australia on the final leg of the 400 free relay.
‘‘It was a change of pace for me to be passed by someone,’’ Thompson said. ‘‘It’s usually the other way around.’’
The Aussies got the upper hand in their spirited swim rivalry with the Americans, winning two of the night’s four races. But the powerful U.S. team claimed five medals in all, more than any other country on the first of eight days at the sweltering outdoor pool.
Thorpe almost missed the 400 free — his best event — when he inexplicably fell off the starting block at the Australian trials, earning an automatic disqualification. But he got in when teammate Craig Stevens gave up his spot.
The two are rooming together at the Olympic Village. ‘‘I’m glad I’ll be able to share it with one of my friends,’’ Thorpe said.
The Thorpedo barely held off another countryman, Grant Hackett, to win in 3:43.10. Arcadia High School graduate Klete Keller took bronze for the second straight Olympics, setting an American record of 3:44.11. He led the race for the first 150 meters before the Aussies regained control.
Still, Keller was pumped about the U.S. men’s fast start. ‘‘It gets us all really excited. It’s such a great medal haul,’’ he said. "We came back with some real nice hardware. It just shows we’re going to do even better here than we did at our trials, which was one of the most successful meets in our history. If this keeps on going, we’re going to have a pretty awesome Olympics.’’
Thompson, 31, had a chance for her ninth gold when she dove into the water for the anchor leg with a lead of nearly four-tenths of a second.
But the greatest relay swimmer in U.S. history couldn’t hold it. Jodie Henry passed Thompson after they made the final turn nearly in unison, touching the wall in 3:35.94 to break the world record of 3:36.00 set by Germany (2002).
The winning team included Alice Mills, Lisbeth Lenton and Petria Thomas, but it was Henry who did the bulk of the work. She swam nearly a second faster than Thompson with a stunning time of 52.95 for the final 100.
Thompson swam her 100 in 53.77 — best of the American swimmers and enough to give the team a national record of 3:36.39. The Netherlands took bronze.
‘‘We were so close,’’ Thompson said. ‘‘We set a new American record. I think that’s pretty cool.’’
In the night’s other final, Yana Klochkova of Ukraine won her second straight 400 individual medley at the Olympics, holding off American Kaitlin Sandeno by just the length of a hand.
Klochkova became the first two-time winner of the women’s 400 IM in Olympic history. The world-record holder took gold in 4:34.83 — just 12-hundredths of a second ahead of Sandeno.
Sandeno still set an American record, while Georgina Bardach of Argentina claimed the bronze.
‘‘It’s my best time by 5 1/2 seconds,’’ Sandeno said. ‘‘I wasn’t even upset that I got outpunched.’’
The American women have won the last three 400 free relays at the Olympics — each time with Thompson swimming the anchor leg. It didn’t work this time, with Thompson failing to hold the lead given to her by Kara Lynn Joyce, Natalie Coughlin and Amanda Weir.
Thompson still managed to tie the record for most career swimming medals. She’s now got 11, equaling the mark already shared by Spitz, Matt Biondi and Carl Osburn. The only knock on Thompson is that most of those medals have come in relays. Her only individual prizes are silver and bronze, both in the 100 freestyle.
She has a couple of chances to erase that blemish in Athens, earning spots in the 50 free and 100 butterfly. But she’s not considered a strong medal contender in either.