The 26-year-old increased her record world and Olympics medals tally to 37, including 23 world golds.
Biles posted a total of 14.800 in the balance beam final for her impeccable routine ahead of China's Zhou Yaqin with 14.700.
Brazilian Rebeca Andrade, who beat Biles on Saturday to gold in the women's vault, posted 14.300 for bronze.
The American claimed her second gold of the day in the floor final with 14.633, 0.133 points ahead of second-placed Andrade.
Brazilian Flavia Saraiva completed the podium with a score of 13.966 for her first individual medal at the worlds.
"I wasn't too worried about medal count or medal colour," Biles said. "I just wanted to go out there and do my routines again. It doesn't matter if I'm going to get up on the podium or not, that wasn't something I cared about. I just wanted to compete confidently again.
"I had to prove to myself that I could still get out here and twist. I could prove all the haters wrong, that I’m not a quitter. As long as I’m out there twisting again and finding the joy for gymnastics again, who cares?"
Biles led the U.S. women's team to gold before taking a milestone sixth all-around title. She also won gold on balance beam and floor exercise after clinching silver on vault.
Elsewhere, Jake Jarman earned Britain's first gold of the competition by winning the men's vault final earlier on Sunday to become world champion for the first time in his career.
"I was super nervous going into this competition. I don't know why. I kept telling myself, 'just enjoy it, just enjoy it, anything can happen', but I still got nervous,” Jarman said.
The 21-year-old finished ahead of American Khoi Young who took silver to add to his second place in the pommel horse and bronze in the team event.
Germany's Lukas Dauser won the men's parallel bars final while Japan's Daiki Hashimoto took gold in the horizontal bar.