The 20-year-old is number 27 on the annual list after amassing a fortune of $900m (£681m) in less than three years, according to the magazine.
Most of her wealth comes from her make-up company Kylie Cosmetics, which has now sold more than $630m (£475m) worth of products.
Forbes has estimated that that the company is worth $800m (£600m).
Reality TV star and model Kim Kardashian West congratulated her half sister on Twitter and posting the Forbes cover featuring Jenner in a dark suit above the headline "America's Women Billionaires".
She later repeated the post, writing: "Wait I'm posting this again just because! Billion dollar baby!"
Kardashian West herself was placed at joint 54th on the Forbes list alongside author Danielle Steele and businesswoman Janice Bryant Howroyd, with an estimated wealth of $350m (£260m).
Jenner was quoted by Forbes as saying that she owed much of her success to her presence on social media saying: "I have such easy access to my fans and my customers."
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She has more than 25.5 million Twitter followers and 110 million on Instagram, while her company also has 16.5 million on the photo sharing app.
Jenner was ranked higher than singers Madonna, Beyonce, Celine Dion and Barbra Streisand.