Michael Phelps has broken the world record in the 100-meter butterfly at the U.S. national championships.

The 14-time Olympic gold medalist swam the two-lap final in 50.22 seconds at the Indiana University Natatorium on Thursday night. He lowered Ian Crocker’s mark of 50.40 set at the 2005 world championships in Montreal.

The “best swimmer in the world” Michael Phelps was beaten, for the second time, at the Charlotte UltraSwim, losing to French star in the 100-meter freestyle Sunday night.

Phelps touched nearly a full second behind Bousquet, world-record holder in the 50 free, after losing his first final in nearly a year the previous night. Aaron Peirsol beat Phelps in the 100 backstroke.

Bousquet went out strong, ensuring he had a big enough lead to hold off Phelps at the end, even as the the man who has won more Olympic medals than anyone experimented with a new straight-arm stroke that is supposed to provide more speed.

The French swimmer touched in 48.22 seconds, while Phelps finished second in 49.04.

“The biggest thing that killed me were my turns and my finishes,” said Phelps, who holds the American record in the 100 free at 47.51. “I’m not disappointed with that time, but the finish was awful. There’s small things I need to work on. But overall, it was a good meet.”

On Wednesday, Phelps swam into history as the winningest Olympic athlete ever with his 10th and 11th career gold medals and five world records in five events at the Beijing Games.

A day after joining fellow Olympians Mark Spitz and Carl Lewis with gold medal No. 9, Phelps set a standard all his own when he won the 200-meter butterfly. An hour later, he swam the lead off of a runaway victory by the U.S. 800 freestyle relay team, which destroyed the old world mark in becoming the first team to break the 7-minute barrier.

Seemingly immune to fatigue, he set a blistering pace of 1 minute, 43.31 seconds that got the Americans rolling toward a winning time of 6:58.56.

Michael Phelps opened his epic quest for a record eight gold medals in dominating fashion by smashing his own world record in the 400-meter IM. With President Bush in the bleachers, Phelps dominated his first event of the Beijing Olympics on Sunday morning, beating his own world record and all chances for his challengers with a mark of 4 minutes, 3.84 seconds in the 400-meter individual medley. One down, seven to go in Phelps’ quest to break Mark Spitz’s record of seven gold medals.