A day after locking up her second straight World Cup overall championship, the American secured her fifth season title in the slalom.
After becoming just the fourth American to win multiple overall titles with a third-place giant slalom finish on Friday, Shiffrin now stands all alone in second with the most women's technical event (GS, slalom) wins at 37.
Saturday's win was Shiffrin's 31st World Cup slalom victory, and after wrapping up the overall World Cup title with a third-place finish in Friday's giant slalom, she now has won the World Cup slalom title five times: 2013, 2014, 2015, 2017, 2018.
Shiffrin formally won the discipline title as soon as the only remaining challenger, Petra Vlhova, failed to get the top-two result which the Slovakian skier needed in the penultimate event of the season.
In the men's downhill in Kvitfjell, Beat Feuz finished second behind Thomas Dressen to stretch his lead over Aksel Lund Svindal to 60 points.
Also, getting her 11th win of the season was a personal best, though Schneider (14 in 1988-89) and American teammate Lindsey Vonn (12 in 2011-12) won more races in a single season.
Norway's Ragnhild Mowinckel claimed her first World Cup victory having won two silvers at the Olympics.
Shiffrin had not raced since the Olympics.
Shiffrin is now tied for fifth on the women's career World Cup wins list with Swede Anja Pärson.
"For sure I have a big lead", Shiffrin said. PyeongChang gold medalist Frida Hansdotter of Sweden was third. Her last race was at age 26.
However, she failed to win a race after triumphing at a night slalom in Flachau, Austria, on January 9.