Rihanna has become the youngest self-made billionaire woman in US, as per Forbes. The 34-year-old has a net worth of $1.4 billion. She was ranked 21st overall in 'America's Richest Self-Made Women' list and is the only billionaire under 40 on the list. After Rihanna, the next-youngest billionaire on Forbes' list is 41-year-old Kim Kardashian, with $1.8 billion net worth.