The 24-year-old Swede was 6.64 seconds – an eternity in alpine skiing – ahead of second-placed Anna-Maria Rieder, Germany.
It's tough when it's steep all the way and your leg gets no rest, but it worked out and I'm happy, she says to SVT after the race.
The Frenchwoman Aurelie Richard came third.
Årsjö has won six out of seven World Cup competitions this season and is on her way to winning the overall World Cup for the second consecutive season.
Wednesday and Thursday offer new opportunities for victory, when two more slalom competitions are held in Feldberg.
