1. Kim Jong Un, 33, is the leader of North Korea. He has been in power since his father's death in 2011, and has worked to expand the country's nuclear weapons program, gaining even more notoriety in his recent clashes with Trump.
2. Mohammad bin Salman, 32, is the Crown Prince of Saudi Arabia and the king's designated successor. He currently serves as Saudi Arabia's defense minister and has introduced a plan to remake the country's economy.
3. Mark Zuckerberg, 33, is the founder and CEO of Facebook. The Zuckerberg-led social network is used by billions of people and has turned him into the fifth richest person in the world.
4. Sebastian Kurz, 31, is leader of the conservative Austrian People's Party and is expected to become the next chancellor of Austria. When he takes over as chancellor, Kurz will become the youngest national leader in the world.
5-6. Ivanka Trump, 35, and Jared Kushner, 36, are President Donald Trump's daughter and son-in-law, respectively. The couple are two of his closest advisers.
7. Sheikh Tamim bin Hamad Al Thani, 37, is the Emir of Qatar. The British-educated ruler took over as the nation's leader when he was 33, following his father's abdication.
8. Jigme Khesar Namgyel Wangchuck, 37, is the king of Bhutan. The king is reportedly well-loved by the Bhutanese, and has mixed the traditional and modern during his reign.
9. Prince William, 35, is currently second in line to the British throne. Titled the Duke of Cambridge, his marriage to Kate Middleton garnered world attention, and he now has two children with her and a third on the way.
10. Sam Altman, 32, is the president of Y Combinator, Silicon Valley's largest startup incubator. Altman has laid out his vision of tech-powered future, and is commenting more frequently on politics and his plan for the US's future.
11. LeBron James, 32, is one of the most dominant athletes in the world. The star basketball player has comically lampooned his own image on TV and in movies, and is outspoken on social and political issues.
12. Beyoncé Knowles-Carter, 36, is one of the best-selling musicians in history and a cultural icon known worldwide by just her first name. Beyoncé has also starred in several major movies, and entered the political realm with endorsements and calls to action.
13. Malala Yousafzai, 20, is a Pakistani activist and the youngest ever Nobel Prize winner. Awarded the Nobel Peace Prize for her work towards women's education rights, Malala is currently attending the University of Oxford.
14. Oyo Nyimba Kabamba Iguru Rukidi IV, 25, is the king of Toro, a kingdom in Uganda. He has been the kingdom's ruler since he was a toddler, after his father died in 1995.
15. Enrico Carattoni, 32, is the recently elected co-Captain Regent of San Marino, a tiny republic surrounded by Italy. His six-month term will last until April 2018.