Ligety turned in a combined two-run time of 2 minutes, 28.92 seconds Friday, beating Austria's Marcel Hirscher by 0.81 seconds and Manfred Moelgg of Italy by 1.75 seconds.
The U.S. veteran previously captured the super-G and super-combined at the championships in Schladming, Austria. The International Skiing Federation said in a written statement the last skier to win three golds at a world championship meet was Austrian Toni Sailer in 1958.
"It has been a crazy week," Ligety said. "I am now joining some legends of the sport. That's just incredible."
Hirscher, the overall leader in the men's World Cup points race, has been battling back trouble and said he was happy to make the podium after being cheered on by an estimated 35,000 people in his home country. "The atmosphere was just amazing although it was one of the most difficult races in my career," he said. "I gave all I could and must look really worn out right now."