The list also revealed a record 46 billionaires were under age 40, including 24-year-old Snapchat founder Evan Spiegel, 38-year-old Uber co-founder Travis Kalanick and 30-year-old Facebook founder Mark Zuckerberg.
See also:
• Forbes Rich list: Gates still tops world rich list with $79b
• Forbes Rich List: New Zealand's richest man Graeme Hart drops on billionaires list
Serial space entrepreneur Peter Diamandis this week told the Australian Business Insider that the first trillionaire was likely to make their fortune in the space industry.
"Space is infinite, it's where we go next in all directions, the future of humanity."
Diamandis said he has started and co-foudned 17 different companies including one focussed on prospecting near-earth asteroids.
"These asteroids are trillion dollar assets .
"They are everything that we hold of value on earth - metals, minerals, real estate and I think the first trillionaire is going to be made in space."
Microsoft co-founder Bill Gates retained his number 1 spot on the Forbes list for the second consecutive year with an his net worth rising to US$79.2 billion in 2015 from $76 billion last year.
Gates has topped the list for 16 of the last 21 years.
Mexican telecommunications mogul Carlos Slim Helu was in second place with a net worth of $77.1 billion. He topped the list in 2013.