Mexico's Carlos Slim remains the world's richest man for the fourth year in a row, according to Forbes, while Warren Buffett dropped out of the top three for the first time since 2000.
Zuckerberg saw his ranking drop 31 spots as his net worth declined by US$4.2 billion. He is now worth US$13.3 billion.
Irishman Denis O'Brien, 54, who chose Jamaica as headquarters for his powerhouse telecoms operation, Digicel, is now worth US$5.2 billion and is the second-richest person in Ireland. He sits at No. 233 on the Forbes list. He is topped in Ireland by construction magnate Pallonji Mistry, 83, whose net worth amounts to US$10.5 billion.
A record 1,426 people around the world made Forbes magazine's latest annual tally of billionaires, up 16 per cent from last year.
Their average net worth was US$3.8 billion, rising three per cent from 2012.
The total net worth for the list's billionaires was US$5.4 trillion, compared with $4.6 trillion a year ago.
The US continued to house the most billionaires in the world, with 442 of them. It was followed by the Asia-Pacific region, with Europe rounding out the top three.
There were 210 new faces on the list, with Forbes saying many were helped by rebounding equity markets and strong consumer brands.
Slim's net worth increased to US$73 billion from US$69 billion a year earlier. Bill Gates of Microsoft Corp held on to second place with a net worth of US$67 billion.
Berkshire Hathaway Inc's Buffett slipped to the fourth spot with a US$53.5 billion net worth. Buffett was surpassed by Spanish clothier Amancio Ortega, who jumped two spots from 2012 with a net worth of US$57 billion.
While Buffett dropped in the rankings, he added US$9.5 billion to his net worth — making him the second-biggest gainer of the year. The largest gainer was Ortega, who added $19.5 billion to his net worth.
There were 138 women on the list, up from 2012's 104. Liliane Bettencourt, whose family owns a stake in L'Oreal, is the world's richest woman with a net worth of US$30 billion.
Brazil's Eike Batista had the biggest drop in his net worth, with it declining US$19.4 billion to US$10.6 billion.
There were 60 people that dropped off the list entirely, including Zynga's Mark Pincus and former Chesapeake Energy CEO Aubrey McClendon.