Ligety finished in 1 minute, 23.96 seconds, nipping Gauthier de Tessieres of France by 0.20 of a second and Norway's Aksel Lund Svindal by 0.22 ticks.
"I knew I would be good enough to win a medal on this hill, but a gold medal is ... almost unbelievable," said Ligety, whose best finishes in the super-G this season were two fourth places.
The door was opened for Ligety when the veteran Svindal made a slight mistake in the home stretch of an otherwise solid run. Svindal leads the overall World Cup super-G points standings and is second in the overall race.
Tessieres' presence on the podium was also a bit of surprise. It was his first top three finish of the season, and he was only entered in the super-G a couple of days ago when teammate Johan Cleary was scratched with an injury.
The race also knocked Norway's Kjetil Jansrud out of action. Jansrud, who was sixth in the World Cup super-G standings and No. 8 in the overalls, finished the race but was diagnosed with a torn ligament in his left knee.