18) Marie Besnier Beauvalot (Age: 34; Net worth: $2.5 billion)

Marie inherited French dairy behemoth Lactalis along with her siblings. Together they own 100 percent of the company which their grandfather founded in the 1930s. They are working towards expanding the company internationally. Lactalis produces popular President brie. SEE ALSO: Top 10 richest teens in the world – Under 18 (With Pictures)