Shiffrin, 18, posted two runs of under 58 seconds at Levi, Finland, Saturday and breezed to a 1.06-second win over German veteran Maria Hoefl-Riesch.
"Maybe I was a little bit lucky in the first run, I can't even really remember it," Shiffrin said. "I just wanted to treat the second run like its own race and really hammer it. I was in the gate and like, 'No mercy, charge down this course' and I think I did."
It was the fifth career World Cup win for Shiffrin, who turned in a combined-run time of 1 minute, 55.07 seconds. Hoefl-Riesch, who has three slalom victories at Levi on her resume, was clocked at 1:56.13 and Slovenia's Tina Maze placed third with a 1:56.68. Austrian rookie Christina Ager was an impressive fourth in her first career World Cup start with a time of 1:56.73.
Shiffrin won 100 World Cup points for her victory, and was also awarded an actual Finnish reindeer, a 6-month-old calf she named Rudolf. "Who wouldn't want to get a reindeer?" she joked. "I remember being 5 years old and 'Rudolf the Red-Nosed Reindeer' was my favorite song."