Forbes' 2016 list of the World's Billionaires includes 1,810 billionaires, down from a record 1,826 a year ago.
Their aggregate net worth is $6.5 billion (roughly Rs. 43,946 crores), $570 million (roughly Rs. 3,853 crores) less than last year.
Gates remains the richest person in the world with a net worth of $75 billion, despite being $4.2 billion (roughly Rs. 28,395 crores) poorer than a year ago. He has been number one for 3 years in a row and topped the list 17 out of 22 years.
Forbes said Ambani, 58, has retained his position as India's richest person despite shares of his oil and gas giant Reliance Industries taking a hit due to lower oil prices.
He is ranked 36th on the list with a net worth of $20.6 billion (roughly Rs. 1,39,275 crores), the magazine said, adding that "the $62.2 billion (roughly Rs. 4,20,531 crores) (revenues) firm is likely to resume buying crude oil from Iran after the lifting of sanctions."
Occupying the second spot on the list is Spanish billionaire Amancio Ortega, founder of closing retail giant Zara and the richest man in Europe.
On the third spot is billionaire philanthropist and Berkshire Hathaway CEO Warren Buffett, Mexican billionaire Carlos Slim Helu (4) and Amazon CEO Jeff Bezos (5).
Ambani leads a pack of 84 billionaires from India, with pharma magnate Dilip Shanghvi (rank 44 and $16.7 billion (roughly Rs. 1,12,907 crores) networth), Wipro Chairman Azim Premji (55 with $15 billion (roughly Rs. 1,01,414 crores) networth) and HCL co-founder Shiv Nadar (88 and $11.1 billion (roughly Rs. 75,046 crores) networth) coming in among the top 100 billionaires.
Other prominent Indian billionaires include ArcelorMittal Chairman Lakshmi Mittal (135), Bharti Airtel's Sunil Mittal (219), Ports and power magnate Gautam Adani (453), matriarch Savitri Jindal (453), Bajaj Group's Rahul Bajaj (722), Infosys chairman emeritus N R Narayana Murthy (959) and Mahindra Group's Chief Anand Mahindra (1577).
Also making to the list is investor Rakesh Jhunjhunwala on the 1011 rank, Infosys cofounder Nandan Nilekani (1121), Former Amazon executive and Flipkart founder Sachin Bansal (1476) and pharma company Wockhardt chairman Habil Khorakiwala (1694).
Forbes' 221 people fell off the list, while 198 newcomers joined the ranks of billionaires in 2016.
Apart from Gates, Buffett held steady in the top 20.
Facebook founder Mark Zuckerberg had the best year of all billionaires. The 31-year-old added $11.2 billion (roughly Rs. 75,722 crores) to his fortune and moved up to No. 6 from 16. He and Amazon's Jeff Bezos both make their first appearance in the top ten of Forbes' annual ranking of the world's wealthiest.
In another first, billionaire from China's mainland, Wang Jianlin, whose company owns AMC Theaters climbed into the top 20.
Among the most notable newcomers are Cameron Mackintosh, the first theater producer to make the billionaire ranks; WeWork's Adam Neumann and Miguel McKelvey and Pinterest's Ben Silbermann and Evan Sharp.
Neumann, Silbermann and Sharp are three of a record 66 billionaires under the age of 40.
The youngest billionaire in the world is a 19-year-old Norwegain heiress, Alexandra Andresen, who has a 42 percent stake in her family's business.
Her sister Katharina is second youngest, just 20. Forbes said another new entrant worth mentioning is Zhou Qunfei, whose $5.9 billion (roughly Rs. 39,889 crores) fortune from smartphone screens is enough to make her the richest self-made woman in the world.
She is one of 190 women in the list, down from 197 last year.
The US has 540 billionaires, more than any other country in the world, followed by mainland China with 251 (Hong Kong has another 69) and Germany with 120. Russia has 77, ten-figure fortunes, 11 fewer than last year, while Brazil is down 23 to 31.
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