The 21-year-old has reached the milestone two years earlier than Facebook founder Mark Zuckerberg.
It's all thanks to the booming cosmetics company she founded just three years ago.
The 21-year-old, who is the half-sister of reality television stars Kim, Khloe and Kourtney Kardashian, has made it onto the annual Forbes list of billionaires.
She has a net worth of $1bn (£759m).
Facebook founder Mark Zuckerberg was 23 when he made onto the billionaire's list.
Jenner debuted her brand Kylie Cosmetics online in 2015 with $29 (£22) lip kits containing lipstick and lip liner.
The company did an estimated $360m (£273m) in sales, according to Forbes.
Jenner, who has a one-year-old daughter, owns 100% of the company.