Jeff Bezos leapfrogged Gates, who has been the richest man on the planet since 2013, after a rise in the share price of Amazon ahead of its latest results due later on Thursday.
According to a real-time billionaires index compiled by Forbes, the rise pushed the value of Bezos’s fortune to $91bn (£69bn) – compared with Gates’ wealth of $90bn. Their riches are calculated on the share prices of their respective companies.
Bezos – born in Albuquerque, New Mexico, in 1964 – has already used the wealth he has amassed to buy the Washington Post and invest in space travel through Blue Origin, a company he founded in 2000.
He founded Amazon in 1994 when he sold books from his garage in Seattle before its business lines expanded in to a wide range of other products and captured the global mood for online shopping. Amazon now accounts for 43% of everything sold online in the US.
Its shares have soared this year, gaining 40% – which helps to boost Bezos’s wealth as he owns 17% of the company.
At the start of 2017, Bezos was ranked fourth richest in the world, behind Gates, the investor Warren Buffett and Amancio Ortega, who founded Inditex, the company behind retailer Zara.
The share price rally comes despite accusations by Donald Trump during the US election campaign when he accused Amazon of “getting away with murder, tax-wise”. He said Bezos was using the Washington Post for “political influence”.
Amazon floated on the stock market in 1997. Bezos reprints the letter he sent to shareholders that year in every annual report, insisting it is only Day 1 for the company and pledging to focus on the long-term and being the market leader and not short term.