The triple all-around champion took her overall gold medal haul at the worlds to nine after obliterating the opposition with a score of 15.358, more than a point ahead of second-placed Dutchwoman Sanne Wevers.
While wobbles and falls littered the programmes of the seven other finalists, with four gymnasts slipping off the beam, Biles was rock solid as she spun around 900 degrees on her right toes.
She flew through her other acrobatic flips and when she nailed her full-twisting double back somersault dismount, it was game over for the others as Biles secured her second successive gold in the discipline.
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Germany's Pauline Schaefer finished third.
(Reporting by Pritha Sarkar, editing by Tony Jimenez)
