According to Bloomberg's daily billionaire index, Bezos' net worth reached US$105.1 billion Monday.
He and Bill Gates traded the title of world's richest person several times a year ago.
Gates, 62, would have a net worth of more than $US150 billion if he'd held onto assets that he's given away, largely to the Bill & Melinda Gates Foundation.
Companies Jeff Bezos Swipes Title as Richest Man in the World
Amazon's share price, and therefore Bezos' net worth, has jumped significantly since September. He lost the title later in the day when Amazon's stock dropped, returning him to second place with a net worth just below $90 billion.
Bezos' other holdings include The Washington Post and Blue Origin, a private space travel business that intends to take tourists into space. According to publicly disclosed donations, Gates has given away 700 million shares of Microsoft - worth almost $62 billion at today's value - and close to $3 billion in cash over the years.
Bezos' wealth peaked as Amazon stock prices have climbed on the back of strong holiday shopping performance.
Bezos came under fire a year ago when The New York Times questioned his level of philanthropic giving.More news: Roy Moore Accuser's House Burned Down, And You Know What People Wondered