Hirscher, who is bidding for a third successive overall alpine World Cup title, was the quickest from the first run in Italy after posting a time of 1:18.14minutes.
However, the Austrian almost blew his third win across all disciplines this season and second in a row in the giant slalom, halfway down the course when he appeared to lose his legs.
However Hirscher managed to pull off the near impossible and maintain his balance before doing enough to take victory in an overall time of 2:37.45.
Alexis Pinturault had previously put in a fine run but he was 0.35 seconds shy of Hirscher while Ted Ligety was also impressive but was 0.23 adrift of the Frenchman.
Hirscher leads the giant slalom World Cup standings by 60 points ahead of Ligety while he is 95 behind Aksel Lund Svindal, who was 13th in Alta Badia, in the overall rankings.
Meanwhile across Europe in Val d'Isere, Tina Weirather's own fine season continued as she took her second win of the season, first in the giant slalom and sixth top-three finish in total.
Weirather won by almost a second ahead of Lara Gut, her 2:24.10 time 0.73 better than the Swiss skier's while Maria Pietilae-Holmner was third with 2:25.05.
Jessica Lindell-Vikarby, sixth in Val d'Isere, leads the giant slalom World Cup ahead of Weirather but she leads the overall standings by 27 points ahead of Gut.