Vonn was tied with Phil Mahre of the United States with three overall World Cup titles. Moser-Proell won six overall titles in the 1970s, and Luxemburg's Marc Girardelli has five.
"I don't know what to say," an emotional Vonn said. "I just wanted to have two aggressive runs today. I felt like I had nothing to lose and I was having fun. I'm just really excited, I'm thrilled. It's crazy."
Vonn won the overall title from 2008-2010. Last season Vonn just missed out on another, finishing three points behind Maria Hoefl-Riesch. The German won the overall title after the giant slalom race at the Lenzerheide finals was canceled because of soft snow conditions.
"It's definitely a lot less stressful to clinch the overall title before the finals. Last year at the [Lenzerheide] finals, I might have lost a few years of my life," Vonn said with a smile.
With this overall title, Vonn surpasses Croatian Janica Kostelic, Swiss Vreni Schneider and Austrian Petra Kronberger, who all won three overall cups during their careers.
Vonn has 1,808 points for the season and, with five World Cup races remaining, looks set to achieve her goal of become the first woman to surpass 2,000 points. In 2006, Kostelic set the overall points record for women, amassing 1,970 points to claim the crystal globe.
"Anything is possible, but it's going to be really difficult," Vonn said. "I'm going to have to execute in every race and seize the opportunity like I did today.
"I've got three big chances to make the top three in the downhill, super-G and the GS [in Schladming]. But I'm going to have to execute and make no mistakes."
Vonn won her 52nd World Cup race with only her second victory in giant slalom. She won the season's opening giant slalom in Soelden in October to become the fifth woman to win a World Cup race in all five disciplines.
Vonn is third on the all-time list for World Cup wins behind Moser-Proell (62) and Schneider (55).
"This season, I've really found my rhythm in GS. It's been a great year," Vonn said.