Vonn ignored a bruised right knee after crashing in Thursday's giant slalom to win the final super-G and make sure of the overall title with one race left in the season.
She also notched up her 33rd career win, a US record for both men and women - beating Bode Miller's 32 - and extended her own national record of wins in a single season to 11.
"My jaw is still hanging on the ground," Vonn told Reuters after holding off a strong late challenge from Germany's Maria Riesch, who beat her in the downhill on Wednesday and finished second in Thursday's giant slalom to prolong the title race.
"I was so nervous today because if Maria had finished second then I would have had to get in the top seven or the World Cup could slip through my fingers.
"It was a dream season," added Vonn, who also won the Olympic downhill gold medal last month.
"To break the US record, to get the gold medal in the downhill, my favorite discipline and all round for the third time, for me doesn't get much better. When you work so hard, it feels so great." The American also won the super-G and downhill trophies, winning six out of eight races in the latter event.
Skiing last on Friday, Vonn had already been assured of the title when Riesch, her only rival and needing a win or second place to maintain her challenge, was pushed out of the top two. Instead of taking it easy, Vonn tore down the Kandahar course to win with a time of one minute 19.30 seconds, 0.16 seconds ahead of Elisabeth Goergl of Austria. Nadia Styger of Switzerland finished third and Riesch ended up fourth.
"As soon as I won the overall, I just thought let's get the US record and just forget about all the injures I've had in the season," said Vonn.
Olympic champion Andrea Fischbacher was involved in a spectacular crash halfway down the course when she was leading.
The Austrian clipped a gate, lost her balance and somersaulted, then slid around 50 meters before coming to a halt. She appeared unhurt and was able to ski down the rest of the course.
Janka wins World Cup to end Swiss wait
Meantime, Carlo Janka won the overall Alpine ski World Cup on Friday, becoming the first Swiss man to take the title for 18 years.
Racing last, Janka won Friday's giant slalom to open up an unassailable 106-point lead over Austria's Benjamin Raich with only Saturday's slalom still to race.
In a rare show of emotion, the usually ice-cool Janka collapsed on the ground and raised his arms in the air after seeing that he was first, setting off a cacophony of cowbells and rattles among the Swiss fans at the finish line.
The last Swiss man to win the title was Paul Accola in 1992.
Raich, champion in 2006, finished eighth to make sure of second place overall for a remarkable fourth year in a row and the fifth time in the last six.
Janka, Olympic champion in the giant slalom, led after the first leg. The 24-year-old produced only the eighth fastest run in the second leg but it was enough to win the race and title.
Ted Ligety of the United States finished joint third with Austrian Philipp Schoerghofer to clinch the giant slalom title for the season.
