The 21-year-old has reached the milestone two years earlier than Facebook founder Mark Zuckerberg.
Kylie Jenner has been named the youngest self-made billionaire of all-time, thanks to the booming cosmetics company she founded just three years ago.
Jenner debuted her brand Kylie Cosmetics online in 2015 with $29 (£22) lip kits containing lipstick and lip liner.
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.
Kylie Cosmetics last year signed a deal with Ulta Beauty Inc to put their products in all of the retailer’s 1,163 US stores. Jenner, who has a one-year-old daughter, owns 100% of the company.
Forbes has said she was both the world’s youngest billionaire and also the youngest self-made billionaire ever.
On their list, Forbes distinguishes between those who inherited much of their wealth and those who made their fortunes themselves.
Jenner is in 2,057th place in the overall list covering all ages, and whether the wealth was self-made or inherited.
She also makes money from endorsements and appearances on cable TV’s “Keeping Up with the Kardashians”.
Forbes put 2,153 billionaires on its 2019 list, down from 2,208 in 2018, and said their total combined net worth was $8.7trn (£6.6trn) down from $9.1trn (£6.9trn) in 2018.
The richest person in the world remained Amazon’s chief executive officer Jeff Bezos, whose net worth increased to $131bn (£99.4bn) from $112bn (£85bn) in 2018, according to Forbes.
Microsoft co-founder Bill Gates remained in second place with an estimated fortune of $96.5bn (£73.3bn), up from $90bn (£68bn) last year
Facebook founder and CEO Mark Zuckerberg dropped three places to number eight, as his fortune fell by $8.7bn (£6.6bn) to $62.3bn (£47.3bn).