Polygamy forms part of Zulu culture and is legal in South Africa, and Zuma, a Zulu traditionalist, has 21 children, according to the presidency website.
“President Jacob Zuma will be formalising his relationship with his fiancée by having a private traditional ceremony this coming weekend,” said Zuma’s spokesman, Mac Maharaj.
The ceremony will take place in Nkandla in KwaZulu Natal province, Maharaj said.
Zuma is also married to Sizakele Zuma, Nompumelelo Ntuli-Zuma and Tobeka Madiba-Zuma. He was previously married to Home Affairs Minister Nkosazana Dlamini-Zuma, and to Kate Mantsho-Zuma who committed suicide in 2000.
Mr Zuma, who leads South Africa’s ruling African National Congress, lives with his three current wives at his rural homestead.
All three were at the politician’s side as he was inaugurated president in 2009.
The trio of spouses are now all officially treated as First Ladies and share Mr Zuma’s official engagements between them.
Last week all were on hand to cut the presidential cake during lavish celebrations for his birthday in Durban.
Mr Zuma, who spent time as a political prisoner under South Africa’s apartheid regime, is also believed to have dated a string of other women.
The polygamist leader faced controversy two years ago after it emerged that he had fathered a child with the daughter of one his close friends.