The chairman of Reliance Industries Ltd is now worth $68.3 billion, beating Warren Buffett's $67.9 billion, according to the Bloomberg Billionaires Index.
Shares of Mr Ambani's Indian corporation have more than doubled since a low in March as its digital unit got more than $15 billion in investments from companies including Facebook Inc and Silver Lake. This week BP Plc paid $1 billion for a stake in Reliance's fuel-retail business.
While Mr Ambani's wealth has jumped -- he became the only Asian tycoon in the high-class club of the world's top 10 richest people last month – Mr. Buffett's fortune dropped this week after he gave away $2.9 billion to charity.
Buffett, the 89-year-old Chairman and CEO of Berkshire Hathaway, saw a fall in wealth after donating more than $37 billion of Berkshire Hathaway Inc. stock since 2006. Buffett, fondly known as the 'Oracle of Omaha', gave away $2.9 billion to charity this week.
Mr Ambani, 63, is now the eighth richest person on the planet, and Mr Buffett is ninth, according to the index, which started in 2012. Also, because of Ambani’s business spread, India has emerged as a hot-spot for M&A this year, accounting for more than 12% of those announced in Asia Pacific -- the highest ratio since at least 1998.