The 25-year-old, who used to represent France and switched to Great Britain in 2018, topped the qualifiers on Tuesday, before dominating all the way through the final, where she came out on top after a tight race.
In the decisive race, Bankes took a comfortable lead after some smart riding in the top section and held on until the finish line, despite a mistake in the final stretch.
"It's pretty amazing, I think I've had a great few days here. It's been a really fun course, it's just amazing to be able to pull all the runs together," Bankes told FIS after the race.
"I think the final was tight racing: unfortunately I made a mistake at the end. It's a shame for Belle (Brockhoff), I'm really sorry for her, it was a really tight race and unfortunately, she crashed out because of me, but I'm happy I managed to stay on my feet and keep it through the line"
Photo-finish in the men's race
In the men's final, Spain's Lucas Eguibar came from behind to pip pre-race favourite Alessandro Haemmerle of Austria at the finish line.
The 27-year-old Spaniard clinched his second individual medal at the Worlds, following a silver on home snow in Sierra Nevada four years ago.
"I can't believe it, I didn't start the season very well and I came here with no really good feelings, but my team made such a good job and I can't believe it, I'm dreaming," 27-year-old Eguibar said to FIS after the race.
19-year-old Eliot Grondin of Canada rounded off the podium.
Haemmerle had the best start, but Eguibar built speed at the bottom of the course and beat the Austrian at the photo finish.
"I was behind, I knew that in the end I was very fast and I just told myself, 'just go, just go, don't think about anything!"