Tesla Inc chief and billionaire entrepreneur Elon Musk surpassed Amazon.com Inc's top boss Jeff Bezos to become the world's richest man, Bloomberg News reported.
Musk has a net worth of more than $188.5 billion, $1.5 billion more than Bezos, the report said.
Musk's personal wealth has been boosted by last year's more than eight-fold surge in the shares of Tesla, which became the world's most valuable carmaker.
He has a 20 per cent stake in the carmaker and about $42 billion of unrealised paper gains on vested stock options, according to the Bloomberg report.
Tesla shares were up as much as 7.4 per cent on Thursday at a record high of $811.61.
The Forbes Billionaires List, however, said Musk still trails Amazon's Bezos by $7.8 billion.
Forbes has a more conservative estimate based on the Tesla stake that he has pledged as a collateral for personal loans. To take that into account, it applies a 25 per cent discount to his shareholding, according to its report in November.
Musk, who co-founded and sold Internet payments company PayPal Holdings Inc, now leads some of the most futuristic companies in the world.
Besides Tesla, he heads rocket company SpaceX and Neuralink, a startup that is developing ultra-high bandwidth brain-machine interfaces to connect the human brain to computers.
He set up the Boring Company to make affordable tunnels below busy city streets for an all-electric public transportation system to avoid the nasty traffic jams in US cities.