Several notable billionaires experienced massive hits to their fortunes Monday as the Chinese generative artificial intelligence startup DeepSeek upended the U.S. stock market, hitting the American AI leader Nvidia the hardest.

The recent AI advances by Chinese upstart DeepSeek could be the beginning of a potential nightmare scenario that Nvidia Corp. Chief Executive Jensen Huang has been worrying about since the chip maker’s meteoric rise.

Nvidia just made history—but not in the way they hoped. The tech giant lost a staggering $600 billion in market value in a single day, thanks to the rise of DeepSeek, a Chinese AI company disrupting the game.