John Collison, 26, ranks as the world’s youngest self-made billionaire, according to the latest compilation of the super-rich by Forbes magazine.
Along with his brother Patrick, the Irish-born entrepreneur founded a San Francisco-based software platform called Stripe for online payments.
The brothers are two of the four billionaires in the world that are still in their 20s.
Mr Collison was only 17 when he founded his first company Shuppa, an online auction management company, which he sold for more than EUR 5 million in 2008.
He is estimated to be worth $1.1 billion while Stripe is valued at $9.2 billion.
He is on record said that there are still opportunities out there for budding entrepreneurs. "It's easy for people to think the best opportunities are taken. I absolutely don't think that is true at all.
He added: "My advice to my younger self would be not to be too OK with the ways the world is broken, and instead see them as opportunities.
"For instance, I don't think anyone's particularly happy with their mobile-phone provider. If a better provider were to come around, I don't think anyone would be particularly surprised."
The Forbes ranking covers 2,043 billionaires around the world, the most in the 31 years the magazine has been tracking them.