Biles, who led the United States to team gold before grabbing all-around gold, produced a pair of stunning vaults to notch a resounding victory over Olympic and world champion Rebeca Andrade of Brazil.
American Jade Carey took bronze.
Biles took control with her opening vault, the Yurchenko double pike now named the Biles II.
Her height off the vault table was astonishing, and even though her momentum carried her back a step on landing, her execution score of 9.4, along with the 6.4 difficulty score for the move so tough no other woman attempts it, earned 15.700.
Biles produced another soaring effort on her second vault, a Cheng, scoring 14.900 for a winning average of 15.300.
Andrade opened with a beautiful Cheng vault that garnered 15.100 points and had a slight hop on landing of her second vault for a 14.833 and an average of 14.966.
Carey was the last of eight finalists and snatched bronze with an average of 14.466, denying North Korea's An Chang Ok.
Biles, clad in shimmering red, gave a big smile as she received another rapturous reception at Bercy Arena.
Her smile was just as big as she saluted the judges after landing her second vault, and she was still smiling as she high-fived coach Laurent Landi.
The US great now owns a total of 40 world and Olympic medals -- 30 of them gold.
She could add to that tally on Monday, when she competes in the balance beam and floor exercise finals, capping her return to the Olympic pinnacle after a bout of the disorientating and dangerous mental block called the "twisties" saw her pull out of most of her events in Tokyo.
