1 Christy Walton & family
$25.3 billion - As of March 2012Source: Wal-Mart, inherit and growingAge:56 , Citizenship: United States
She inherited her wealth from her late husband,John Walton who died in an airplane accident near his home in Wyoming 2005. Repeating her 2010 title as world's richest woman, she got an extra bump in her fortune because of her late husband's early investment in First Solar; shares up nearly 500% since 2006 initial public offering. But bulk still comes from her holdings in Wal-Mart, the retailer founded by her father-in-law Sam Walton and his brother James in 1962. Today Wal-Mart has sales of $405 billion, and employs more than 2.1 million people.