- King Mswati III (18 years old), Swaziland
As a boy, Mswati III attended Masundwini Primary School and later Lozitha Palace School, where he excelled in mathematics and English. He later developed an interest in the military and eventually became the first young cadet to join the Umbutfo Swaziland Defence Force.
Mswati was only a 14-year-old boy at the Sherborne School in London, when his father, the king, died and he was selected by a council of elders as the next king. While he pursued his studies in the U.K., his mother served as regent in his place until he turned 18.
At barely 18 years old, Prince Makhosetive was crowned as King Mswati III of Swaziland and head of the country’s royal family in April 1986. His enthronement earned him the title as the youngest monarch/sovereign in the world at the time of his coronation.