Shiffrin lands blow ahead of Olympics
Mikaela Shiffrin of the US races down the floodlit slope during the first round of the slalom race of the FIS Ski World Cup in Flachau, Austria, on January 14, 2014
The 18-year-old, who was winning in Flachau for a second successive year, clocked a time of 1min 45.83sec over two runs.
Two Swedes completed the podium with Frida Hansdotter second at 0.83sec, and Maria Pietilae-Holmner third at 1.14sec.
Shiffrin, the reigning slalom world champion and winner of last year's World Cup crystal globe in the discipline, already led after the first run, having put in a thundering performance to finish 0.90 sec ahead of Germany's Maria Hoefl-Riesch.
In the second run, she made a few mistakes but nevertheless proved unbeatable, even as the skiers faced poor visibility and rain on the course.
"There were a couple of moments where I thought I was going out... I had to fight," she said after the race, still looking like she could hardly believe her win.
The youngster thus confirmed her dominance in the slalom, with less than a month to go before the Olympics in the Russian Black Sea resort of Sochi.
For Hansdotter, 28, world slalom bronze medallist, this was her second slalom podium in a month after Courchevel.
All her eight career slalom podiums have seen her fill the runners-up spot.
But with Shiffrin in superior form, this was the best result she could hope for on Tuesday.
"Mikaela was skiing really good... I'm happy with second place," Hansdotter said.
The race, which took place in front of a boisterous crowd of 14,300, had been widely expected to be a duel between Austrian veteran Marlies Schild and Shiffrin, 14 years her junior.
Going into Flachau, each had two slalom wins this season.
But with the joint third fastest time after the first run, Schild, who has won a record 35 World Cup slaloms, made a costly mistake, eventually finishing 26th at 5.84sec.
The popular night slalom in Flachau was one of the last opportunities for the skiers to measure themselves against their competitors ahead of Sochi.
Only one other women's slalom is scheduled before the Olympics - in Maribor, Slovenia, on February 2.