Musk, who is CEO of electric car manufacturer Tesla and rocket maker SpaceX, has a net worth of $188.5 billion, which clocks in at about $1.5 billion more than Amazon's Bezos, Bloomberg said, attributing the shift to an increase in the price of Tesla shares.
On Twitter, Musk responded to a tweet about his new standing with two tweets saying "How strange" and "Well, back to work ..."
Musk's been climbing the rankings. In November,as the second richest person when his net worth hit $128 billion.
Although Bezos hasn't consistently held onto the title, hein October 2018 (it also happened briefly in 2017) when his net worth hit $160 billion. Gates had previously held the spot for 24 years.
Neither Musk nor Bezos responded to a request for comment.