10 of the US' youngest billionaires in 2026 — and how they got their fortunes

Forbes published its 2026 list of the top 400 billionaires in the US on Tuesday.

Many of the US' youngest billionaires owe their fortunes to artificial intelligence startups.

Steven Hao, cofounder and CTO of Cognition, is the Forbes 400's youngest billionaire.

New money is in for America's young and rich.

Forbes released its annual list of America's 400 richest billionaires in September, and a record $4.4 billion net worth was required to make the cut.

Just 10 of those billionaires are under 40, up from four on last year's list. And most of them didn't inherit their wealth. The majority of the US' youngest Forbes 400 billionaires — seven of them — got their money from the AI boom as founders.

Of those seven, four come from one company: Anthropic , the AI company founded only five years ago and now valued at $1.5 trillion in the secondary market . Anthropic's seven cofounders all vowed earlier this year to donate 80% of their personal wealth to philanthropic causes.

The other three are founders of Surge AI, OpenAI, and Cognition.

Only one billionaire on the list — Lukas Walton — inherited their wealth from a family fortune. Walton is the grandson of Walmart founder Sam Walton and is also one of two young billionaires who do not live in California. The other, Edwin Chen, lives in New York.

Here are the 10 youngest billionaires in the US.

Lukas Walton, Illinois' richest person, also runs an impact-investing group called Builders Vision and is chair of the Walton Family Foundation's environment program committee.

As of 2024, Walton has donated at least $150 million of his own fortune to his family's environmental program foundation.

After his father, John T. Walton, died in a plane crash in 2005, Lukas inherited roughly a third of his fortune. Forbes' data shows that the Walton family has a combined net worth of $475.6 billion.

Tom Brown is one of Anthropic's seven cofounders and serves as the company's chief compute officer.

He recently mediated Anthropic's standoff with the US over Claude's AI models Fable 5 and Mythos 5. Claude is Anthropic's conversational AI assistant.

Before Anthropic, Brown worked at OpenAI as a research engineering lead and helped introduce the company's GPT-3 language model.

Brown graduated from MIT in 2010, having studied computer science and cognitive science. He cofounded his first company, social club Grouper, in 2011.