The Swiss skier followed up Saturday's giant slalom victory in Hafjell with a win that slashed Norwegian Henrik Kristoffersen's lead in the standings to 47 points with 100 remaining to be won.
Norway's Atle Lie McGrath was second and Norwegian-born Lucas Pinheiro Braathen, who now skis for Brazil, was third.
The final, decisive race of the season is in Sun Valley, Idaho, on March 27th.
France's 2022 Olympic champion Clement Noel, seventh on Sunday, is also in the running mathematically but 86 points behind Kristoffersen, who was fifth on home snow.
The slalom crystal globe is the only one that Switzerland's Marco Odermatt cannot win this season.
Odermatt has already clinched the overall, super-G and giant slalom globes and leads the downhill standings.
"It's still a big gap, so he (Kristoffersen) has to fail a little bit and I have to do something pretty special like today," said Meillard.
"It's going to be a nice fight until the end."