King Mswati III was crowned in 1986 at the age of 18, succeeding his long-serving father King Sobhuza II, who died at the age of 82.
The king, who is known as Ngweyama - "the lion" - often appears in public in traditional dress and has many wives.
He rules by decree and has been criticised for the heavy-handed treatment of opponents.
The king has also been criticised for requesting public money to pay for new palaces and luxury cars.
Protesters angered by economic decline have become increasingly vocal in demanding political reform.
In 2012, King Mswati - who is thought to have a personal fortune of a 100 million dollars - was given a jet aircraft as a present for his 40th birthday, reportedly a gift from friends and development partners.