Ms Fontana took first place in the women’s 500 metres event in Pyeongchang on Tuesday, with Choi Min-jeong of South Korea so close behind it was a photo finish.
Ms Choi was disqualified, leaving Yara Van Kerkhof of the Netherlands and Canada’s Kim Boutin with silver and bronze respectively.
It was Ms Fontana’s first Olympic gold after a silver and four bronzes in previous games.
“It has been a long journey, more beautiful than I had imagined,” she said after doing a lap of honour in tears, with an Italian flag draped around her shoulders.
The effort earned Ms Fontana, who carried the Italian flag in the games’ opening ceremony, the congratulations of Prime Minister Paolo Gentiloni.
Italy also got its first silver of the games on Tuesday: it went to skier Federico Pellegrino in the men’s cross country sprint.
The nation currently has one medal of each colour, thanks to a bronze for Dominik Windisch in the men’s biathlon 10 kilometre sprint.