NEW YORK (BLOOMBERG) - Elon Musk's financial upswing shows no signs of slowing.

The outspoken entrepreneur is now the world's fourth-richest person after Tesla Inc. shares surged 11 per cent on Monday (Aug 17), closing at a record high and boosting Musk's net worth by US$7.8 billion.

The rise vaulted the Tesla co-founder past French luxury tycoon Bernard Arnault, the wealthiest non-American on the Bloomberg Billionaires Index.

Musk's US$84.8 billion fortune puts him within US$15 billion of Mark Zuckerberg, number three on the ranking of the world's 500 richest people.

Monday's Tesla rally is just the latest triumph for the billionaire who only two years ago was sued by the US Securities and Exchange Commission and had to resign as chairman of the electric car maker over rogue tweets.

Tesla shares are up 339 per cent this year, fueled by growing anticipation that the company will be included in the S&P 500 Index.

Musk's Space Exploration Technologies Corp., or SpaceX, is poised to potentially pad his fortune further. The company is close to finalising US$2 billion in new funding that would increase its equity valuation to US$46 billion, Bloomberg reported last week.

Musk's fortune has grown by US$57.2 billion this year, the second-biggest increase on the index.

Amazon.com Inc. founder Jeff Bezos is this year's biggest gainer, up US$73 billion.