Biles' absence cleared the way for Lee -- she edged out Brazil's Rebeca Andrade, who took silver with a 57.298 score.
It was quite the nail-biter leading up to the final round -- Lee actually trailed Andrade before the floor routine ... but once it was all over, it was the Red, White, and Blue at the top of the podium.
Biles and the rest of the USA gymnasts cheered on their teammate from the crowd ... and Lee's parents and family went completely BONKERS after Lee won it all!!!
@Gia_Vang / KARE 11
USA's Jade Carey also competed in the event ... finishing 8th.