The number of billionaires aged 39 or younger who built their own fortunes has soared amid the AI boom, tying the all-time record set in 2021. These are the 40 wealthiest. Read the full story on Forbes: https://www.forbes.com/sites/mattdurot/2025/12/29/40-under-40-the-richest-self-made-billionaires-under-40/ Subscribe to FORBES: https://www.youtube.com/user/Forbes?sub_confirmation=1 Fuel your success with Forbes. Gain unlimited access to premium journalism, including breaking news,