Ligety covered the course at Kranjska Gora in a combined two-run time of 2 minutes, 35.43 seconds, to win the event and the season championship in the giant slalom.
Austria's Marcel Hirscher, the leader in the men's point standings, took second with a 2:35.88, and Alexis Pinterault of France captured third.
Ligety, who has finished on the podium in all seven giant slaloms this season, clinched the season title without having to wait until the World Cup finals next week.
"It's a big weight off my back," said Ligety. "I had an awesome season in giant slalom but Hirscher was with me the whole season. That makes it tough going for the title."