Kuzmina won in a time of 21:06.08 to see off Russia's Olga Vilukhina, who was 19.9 seconds behind. Vita Semerenko of Ukraine took bronze, 21.7 seconds behind the champion.
Overall World Cup leader Tora Berger of Norway finished down in 10th place, more than 33 seconds behind the winner, while fellow favourite Gabriela Soukalová could only manage 29th place, 1:10.7 behind Kuzmina, having registered three faults on the shooting range.
Slovakia’s greatest Winter Olympian
Born in Russia, and the sister of Russian biathlete Anton Shipulin, Kuzmina is now the first female biathlete in history to complete a successful defence of an Olympic title.
Speaking directly after her victory, she was delighted and a little surprised. “I felt the support of the fans here. The whole stadium was cheering for me - thanks, guys. I feel the home atmosphere,” she said. “I don't know how I managed to get myself together and perform like this today.”
On Saturday she had seen her brother narrowly miss out on a podium place in the men’s 10km sprint, which made her win today especially emotional. “This victory was for him, too,” Kuzmina said. “I hope that it inspires him for tomorrow's pursuit.”
Second-placed Vilukhina, who had struggled to be fit in time for Sochi, was delighted to crown her comeback with a medal.
“I'm happy now," she said. “I am bursting with emotions, but I need to control them because another race is coming up and I need to feel strong and to get myself together.”
Widely regarded as her adopted country’s greatest ever Olympian, Kuzmina is the the only Slovak athlete to win multiple medals at the Games, having taken gold in the sprint and silver in the 10km pursuit at Vancouver 2010.