The "baby-faced" Mittal,34, helped cut his company's debt to 30 per cent after orchestrating the mega-takeover of Arcelor.
"Now Mittal is focused on driving growth in hot markets like Brazil, India and China. This year he helped retool his company's strategy in India where the steel market is expected to triple by 2020," Fortune said.
The son of business tycoon Lakshmi Mittal had ranked fourth on the list last year. The young Mittal is also on the board of French firm PPR and earlier this year when his wife bought bankrupt luxury-fashion brand Escada, he had told her to "pursue it like no tomorrow."
Unlike last year when Mittal was the only Indian on the list, this year another Indian is giving him company. Amit Chatterjee, founder and CEO of enviornmental and energy solutions provider Hara, ranks 37th on the list.
Chatterjee, 38, founded Hara two years ago. Today, the California-based company has "20 million dollars from weighty backers like venture capital firm Kleiner Perkins and clients including Coca-Cola, News Corp and Hasbro."
Computer services company Netscape co-founder Marc Andreessen tops the Fortune 2010 list of 40 "youthful movers and shakers" who are under the age of 40. The 39-year old Andreessen is an "A-list" venture capitalist and director at Facebook, Skype and Hewlett-Packard.
On the second spot is Faceboook founder and CEO 26-year old Mark Zuckerberg. With over 500 million users, Facebook is the leading social networking site and has surpassed Google to become the most trafficked site on the web.
"Even as Aaron Sorkin's film, The Social Network, portrays a certain fictional Harvard dropout with a mean streak, the real Mark Zuckerberg has made good on his goals this year: Facebook will pull in more than one billion dollars in revenue as he unveiled a suite of new social tools," Fortune said.
Micro-blogging site Twitter's co-founders Evan Williams and Biz Stone rank 3 on the list.