Eswatini Prime Minister, Ambrose Dlamini, tested positive for Covid-19 a month ago.
Mr Dlamini, 52, had been hospitalised in neighbouring South Africa, the monarchy's government confirmed late on Sunday.
"Their Majesties have commanded that I inform the Nation of the sad and untimely passing away of His Excellency the Prime Minister Ambrose Mandvulo Dlamini," Deputy Prime Minister Themba Masuku said in a statement.
"His Excellency passed on this afternoon while under medical care in a hospital in South Africa."
Mr Dlamini was moved to South Africa on Dec.1, to "guide and fast track his recovery," from coronavirus. At that time, Masuku said Dlamini was stable and responding well to treatment.
He was appointed prime minister in November 2018, following his position as the chief executive officer of MTN Eswatini, or commonly known as Swaziland.