Chinshanlo, who turned 19 four days earlier, was in third place after the snatch but was unstoppable in the clean and jerk, lifting 131 kilograms in her second attempt to better her own world record by 1 kilogram.
She finished with a total of 226 kilograms — a new Olympic record — and 7 kilograms better than Hsu Shu-ching of Taiwan and Cristina Iovu of Moldova. Hsu got the silver medal because of her lower body weight and Iovu got the bronze.
"I want to celebrate the gold medal by drinking a glass of beer," said Chinshanlo, who stands 1.55 metres tall. "Actually, I am only able to drink half a glass."
Chinshanlo became world champion in 2011, breaking China's dominance in the weight class, though she, too, used to be Chinese. She switched nationalities to join the national team of Kazakhstan, where she was born.
Tears rolled down her cheeks as she sang along to the Kazakh national anthem on top of the podium.
Despite her world record, Chinshanlo wasn't completely satisfied with her result. She had loaded 135 kilograms on the bar for her final clean and jerk, but gave up halfway through the lift.
"On the last lift I had a plan to break the record but I failed. I am a bit disappointed," Chinshanlo said.
China's Zhou Jun, a medal favourite, surprisingly made an early departure from the competition after failing her three snatch attempts.
Aylin Dasdelen of Turkey, who was second to Chinshanlo at last year's world championships, was also eliminated after failing to get a result in the clean and jerk. She appeared to injure her right elbow in her second attempt and didn't come out for her third.
"I am 31 years old so I will be retiring from the sport," Dasdelen said after the competition. "This was my dream so I don't want to carry on."