The 18-year-old American obliterated the previous record of 8:07.39 that she set at the 2015 World Championships last August 8 in Kazan, Russia.
“It was exciting,” said Ledecky, who beat the water in triumph when she saw her time. “It’s always exciting when you can get pushed along by a crowd like this in Austin.”
She upstaged superstar Michael Phelps, who blazed to victory in the 200m individual medley to notch his first win over rival Ryan Lochte in the event since the 2012 London Olympics.
Phelps, whose 18 Olympic gold medals include three in the 200m individual medley, powered through the final 25 meters of the closing freestyle leg to win in 1:58.00sec.
Lochte, the current world record-holder in the event, held a narrow lead at every turn but settled for second in 1:58.43.
“Ryan and I have had a lot of great swims with one another,” Phelps said.
“Joking around with him beforehand, I kind of knew we were going to try to battle it out. I knew it would come down to the touch.”
Phelps finished the three-day meet with two victories — including his 100m butterfly win on Friday — and a fourth place finish in the 200m freestyle.
“We have a couple more meets before (Olympic) trials. Hopefully I’ll be better than this,” said Phelps, adding that the lower-key meetings are a chance to assess not only his speed but also technical details such as turns as he continues a comeback aimed at adding to his Olympic legacy in Rio.
Ledecky, who was the youngest member of the US Olympic delegation in London four years ago, is on course to build her Games legacy as well.
She now owns the eight fastest performances ever in the 800m free and nine of the top 10.
She also holds the world record in the 400m free and the non-Olympic women’s event of 1500m free.
In Rio, Ledecky could line up in the 200m, 400m and 800m freestyles — and perhaps even the 100m free, in which she finished second in Austin this week.
“I was feeling good going into it,” said Ledecky, who romped home with Becca Mann a distant second in 8:24.49.
“Whenever I get going like that, I get into a good rhythm with my freestyle. My stroke just feels good the whole weekend once I have one or two really good freestyle swims.”
In other finals on the last night of the meet, Hungary’s “Iron Lady” Katinka Hosszu pulled off a tough double, winning the 200m medley in 2:10.69 shortly after triumphing in 100m backstroke in 59.91.
Singapore’s Quah Zheng Wen won the men’s 200m fly in 1:58.07, coming from fifth at the halfway mark to triumph.