Hoefl-Riesch sailed down the freshly groomed track in 1 minute, 17.84 seconds, to top Tina Weirather of Lichtenstein by 0.31 seconds.
Nicole Schmidhofer of Austria took third by 1/100th of a second over Lara Gut of Switzerland.
Stacey Cook of the United States finished fifth with a 1:18.62. She was followed by Anna Fenninger of Austrian and veteran Tina Maze of Slovenia.
The win was the third downhill victory of the season for Hoefl-Riesch, who leads Weirather in the overall standings by 158 points. Fenninger is in third place.
Hoefl-Riesch was virtually flawless on the course, which received a fresh layer of snow overnight.
"It was not an easy race," she said. ""I knew I had to attack a lot and that's what I did. There were some difficult turns where some girls had big problems. But for me it went fine."
Notable deaths of 2014 [PHOTOS]
UPI Sports Results for September 19, 2014