America's Lenny Krayzelburg also set a world record, the sixth in three days at the Olympic pool, in the men's 100m backstroke.
The 16-year-old Thorpe lowered his own 200m freestyle mark to 1min 46.00sec in yesterday's final just 24 hours after he set the previous standard at 1:46.34, and two days after he shattered the 400m freestyle record.
"I've never experienced anything like this and I don't think I'll experience anything like it for a long time to come." Thorpe said. "I never believed I'd be able to do it, but I have. It's pretty unbelievable to go so fast three nights in a row."
Krayzelburg, the Ukranian-born American, wiped over a quarter of a second off the previous 100m backstroke record set by America's Jeff Rouse at the 1992 Barcelona Olympics to achieve 53.60sec.
"My goal when I came here was to set a world record, but I surprised myself with that time," Krayzelburg said.
There was some confusion as the timing board malfunctioned, but the race referees reviewed the video back-up clock and declared the result.
The electronic scoreboard was still under repair when Thorpe dived in for the start of his final, but the result was clear by the time he finished.
Thorpe, whose perfomances over the past three days have set the swimming world buzzing, said that he would attempt to lower his record even further today by swimming the lead-off leg in the Australian 4x200m freestyle relay team.
After three days, Australia have won five of the six gold medals in the men's events while the US have collected just one, through Krayzelburg.
Krayzelburg, 23, is the reigning 100m and 200m backstroke champion, but had never set a world record.Reuse content