Brazil's Rebeca Andrade won the silver medal and American Jade Carey took the bronze.
The American also impressed with her second effort. She powered down the runway and launched into the Cheng vault, which incorporates a round-off, half-on entry with a one-and-a-half twisting flip to finish. She earned 14.900.
She claimed a comfortable victory at the Bercy Arena with an average of 15.300 points.
Once the result confirmed that she had topped the eight-woman final, a jubilant Biles flashed a huge smile before sharing a hug with Carey.
"I am super excited, I landed my vaults really well, successfully, so I couldn't be more proud of myself for the work I have put in to get to this point," Biles told Eurosport.
Andrade once again had to make do with coming second best to Biles as she also finished second in the all-around final.
"I love that the athletes push me to be my best. We're all out there competing to the best of our ability so it definitely gives me a run for my money," added the champion who now owns an eye-popping 40 Olympic and world medals.
Biles arrived in Paris as the world's most decorated gymnast and she has reached new heights by claiming gold medals in all three women's events contested so far in Paris. She now has 10 Olympic medals overall, with seven of them being gold.
She led the U.S. team to the top of the podium in the team final before claiming a second all-around Olympic title two days ago.
Biles' impact is not only confined to gymnastics as she also sparked a conversation about mental health after pulling out of the Tokyo Games in the middle of the team final three years ago.
Suffering with the 'twisties' - a type of mental block where gymnasts get disoriented during their gravity-defying sequences - Biles took a two-year break from the sport.
Now that she is back, she is once again the dominant force in gymnastics.
"I put in therapy every week and that helps me manage it. I'm going to continue as soon as I go home because it's an important part of my daily routine," she said.
Biles also praised Carey, who made amends for her last-place finish in the Tokyo vault final by winning bronze on Saturday.
"Great day for me and Jade. We're excited about it so I'm sure we'll get some good food to celebrate," Biles said.
Biles can add to her tally further when she competes in the balance beam and women's floor finals on Monday.
