The 20-year-old Lashmanova was behind her Russian teammate throughout the race in which Kaniskina was leading until the finish line was within sight.
"She turned out to be stronger," Kaniskina said of her Lashmanova, and added she has no regrets for keeping the fast paste from start to finish.
"I was planning to go steadily fast and I was doing very well, but at the end it was not good enough," Kaniskina said.
Lashmanova stepped up over the last 300 metres of the race to power past Kaniskina and finish seven seconds ahead of ahead of the three-time world champion after clocking 1 hour, 25 minutes, 2 seconds.
"We are very close in our team so I hope it will be fine and we are friends," Lashmanova said, adding that she did not expect to get gold at the Olympics. Despite good preparations for the Olympics, she said she did not feel up to the task in the lead up to the event.
"It's the highest achievement for me to get an Olympic medal and break the record, but I did not expect it," she said.
Qieyang Shenjie of China claimed bronze.
Qieyang is the first Tibetan athlete China has ever fielded in the Olympic Games. She finished 14 seconds behind the winner.
"I'm extremely honoured to take part as the first representative of the Tibetans at the Olympic Games and to win a medal," Qieyang said.
The 22-year-old athlete comes from a family of Tibetan herders and started running as a kid on the Tibetan plateau and them joined a sports school.
Rachel Seaman of Peterborough, Ont., finished 52nd.
AP Sports writer John Leicester contributed to this report.