The average age of the 2,208 billionaires on the planet is 66, according to Forbes. But, amazingly, there is no shortage of billionaires in their 20s and 30s (relatively speaking, of course). Many of them worked tirelessly to grow their fortune, but that wasn't the case for all of them. Many inherited their incredible wealth — bank accounts, company shares, and businesses were waiting for them when they were born. Who are the youngest billionaires in the world, and how much are they worth? This list of the 20 richest people under 40 will both inspire and madden you. Fun fact: The 63 youngest billionaires in the world are worth $265 billion collectively, according to Forbes, and $61 billion of that is Mark Zuckerberg’s massive share.

Editor's Note: This piece was first published on July 23, 2016. It has been updated throughout.