Prime Minister Sibusiso Barnabas Dlamini of eSwatini, formerly known as Swaziland, has died at the age of 76, the national television announced late Saturday.
The cause of Dlamini's death in a clinic in Manzini, in the middle of the tiny country, was not given.
It came a week after largely symbolic legislative elections were held in the landlocked neighbour of South Africa, a monarchy ruled by King Mswati III.
Almost all candidates are loyal to the king, who appoints the prime minister, can veto any laws, and is himself above the constitution.
Dlamini was the king's close aide, and ran the government twice, from 1996-2003 and from 2008 until his death.
Mswati, one of the world's last absolute rulers, has 14 wives, more than 25 children, and a reputation for lavish spending on private planes and royal palaces while 63 percent of his subjects live below the poverty line.
Without warning or consultation, he changed the country's name to eSwatini ("land of the Swazis") in April.