The dual world and European champion had to pull out all the stops to fight off the strong-finishing Jamieson amid the din of the roaring home crowd to win in a new world mark of 2:07.28.
Gyurta broke the record of 2:07.31 set by Australian Christian Sprenger at the 2009 world championships in Rome. Jamieson took silver in 2:07.43 and Japan's Ryo Tateishi claimed bronze, a full second back in 2:08.29.
"It was a really hard race, in the last 20m I saw Jamieson, he was so fast in the last part," Gyurta said. "It was hard for me, but I managed to do it.
"I can't believe it, it was my dream when I was young (to get the medal and the world record).
Japan's Kosuke Kitajima, going for a third straight Olympic title, was shut out of the medals in fourth.
Jamieson further fuelled a great day at the Olympics for the host nation after gold medals to Bradley Wiggins in the men's cycling road race time trial and rowers Helen Glover and Heather Stanning in the women's pairs.
"It's been a great day, it's really got the ball rolling, I think everyone's been lifted today," Jamieson said.
"We've had a great week in the pool. Fractions of a second away from medals so I am delighted."
The roar from the home crowd was ear-splitting as Jamieson issued his challenge as Britain seek their first gold medal in the pool.
"Again the support tonight was just unbelievable, the crowd bringing us home in the last 50 was something else and I can only thank them for that," he said.
Tateishi said he was sure Japan would get a medal in the final, fortunately it was for him.
"I am happy with that, I expected to get a medal," he said. "It was a tough race, everyone was capable of getting the gold medal and I just did my best.
"I was sure Kosuke or I would get a medal, but I am happy to have got the medal for Japan."
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