The American, already crowned in the Italian resort in 2008 and 2010, took her third victory in one minute 38.25 seconds.
While she struggled a bit on her return to competition last weekend in St Anton, Vonn was back to her best on Saturday, collecting her 58th World Cup victory and her fifth this season in the resort where she had the first podium place of her career.
"I learnt in the past month that you must listen to your body," said Vonn, who took three weeks off. "I'm glad I took that break. It's an important lesson for the rest of my career.
"Today I felt almost back to the level in my best seasons, with the same attitude and determination. It was great relief to see the number one at the bottom because it didn't happen so often lately."
World Cup overall leader Tina Maze continued her unstoppable path towards her first big trophy by finishing second, 0.43 seconds adrift.
The Slovenian now leads nearest contender Maria Hoefl-Reisch by a seemingly unbridgeable 670 points as the German failed to complete the course.
"I made a couple of mistakes but in any case Lindsey was unbeatable today," Maze told reporters. "She was back to her usual self. Downhill is my worst event and I finished second so I can't complain."
Vonn's compatriot Leanne Smith was third, 0.89 off the pace, for her second downhill podium of the season.
It was the third time two Americans had been in the top three in the discipline this season and a great confidence booster for the team as this was the last downhill before the Schladming world championships in two weeks' time.
Vonn, four times the overall cup winner, is comfortably leading the downhill World Cup, a title she has won for the past five seasons.
She will again be the favourite in Sunday's super-G on the same course, a race she has already won four times, though Maze will be seeking her second win in succession in the discipline.