He died on Friday morning after staying in the hospital for weeks due to a problem with his blood glucose levels.
His health took a turn for the worst, the royal house said leading to his death in the early hours of Friday morning.
“On behalf of the Royal Family, we thank the nation for your continued prayers and support in this most difficult time,” a statement from the house read.
He was born on July 14 1948 in Nongoma, northern KwaZulu-Natal, and was the eldest son of King Cyprian Bhekuzulu and his second wife Queen Thomo.
When his father died in 1968, King Zwelithini assumed control of the throne just at the age of 20.
He was not crowned until 1971 after he went into hiding outside the kingdom following a plot to have him killed.
In 2017 the South African monarch, expressed outrage at the scrapping of caning in schools claiming that using the rod on children would “make learners perform well”.
He told a meeting of principals and school governing bodies in a northern KwaZulu-Natal that “This thing of not disciplining our children is letting us down because children are not disciplined.”
King Zwelithini also proposed in 2019 that convicted rapists should be castrated.
He believed that was the best way to end the wave of rape cases in the rainbow nation.
The King was quoted as saying that his proposal “would end this thing (rape).
“This should be done in a way that would show the world that the Zulu nation does not tolerate this shame,” he said to his subjects at a celebration.
The king said the castration would be carried out by “Men like us”.
King Zwelithini was the longest-serving monarch of the Zulu Kingdom, his reign spanning over five decades.