Forbes estimates that Mr Bezos, 54, who founded the online retail giant in 1994, is worth $112bn, up $39bn in last year – the biggest one-year gain ever.
Meanwhile, US President Donald Trump has tumbled more than 200 places down the rankings thanks partly to a fall in some New York property values.
Mr Bezos has seen his fortune swell over 12 months in which Amazon’s share value has nearly doubled.
Last month Amazon reported a 28% rise in annual profits to just over $3bn.
Mr Gates, who has been the richest person on the Forbes list for 18 of the past 24 years, has slipped to second behind Mr Bezos even though his net worth increased by $4bn to $90bn.
The 62-year-old, who co-founded Microsoft in 1975, has given away much of his wealth and has set up a charitable foundation with his wife to improve global health.
Warren Buffett, 87, the world’s best known investor – whose stock picks and market commentary are closely followed – is number three on the list with $84bn.
Fourth on the list and the highest from outside the US is France’s Bernard Arnault, 69, and his family, who are behind the LVMH luxury goods empire, which includes brands such as Louis Vuitton, Christian Dior and Moet & Chandon. Their fortune stands at $72bn.
Mark Zuckerberg, the Facebook founder and boss, is fifth on $71bn.
At 33 he is easily the youngest of the top five.
Further down the list Donald Trump, worth $3.1bn, has seen his fortune fall by $400m as he slipped 222 places in the ranking to number 766 – partly due to a fall in the value of midtown Manhattan property and declining revenues at some Trump golf resorts.