Chinese shooter Yi Siling collected the first gold medal of London 2012 after winning the 10m air rifle - less than 12 hours after the opening ceremony had finished.
The 23-year-old world number one trailed Sylwia Bogacka until three shots from the end of the final, when the Pole's wayward effort condemned her to silver.
China's Yu Dan picked up bronze ahead of 2008 Olympic champion Katerina Emmons of the Czech Republic, who was fourth.
"I'm very happy. I want to say thanks to China, and to my mother and father," said Yi after receiving her medal from International Olympic Committee chairman Jacques Rogge.
"I'm very excited and happy. I have been shooting since I was 13 years old.
"I've been up since 5am this morning. There was a lot of pressure on me. I think my life will change."
In the men's 10m air pistol, gold went to Jin Jong Oh of South Korea.
The 32-year-old, a silver medallist in the same event in Beijing four years ago, went one better by narrowly holding off Italy's Luca Tesconi, with Serbian Andrija Zlatic taking bronze.
Jin said: "I am very happy because it is a first gold medal for Korea, and personally it is very meaningful.
"I think getting off to a good start is important and I hope this medal will be a spur and inspire Team Korea to more success at these Games."