Mbabane - South Africa's deputy president, Jacob Zuma, will marry a niece of Swazi King Mswati III, making Sebentile Dlamini the fourth woman he weds.
"Zuma's family brought 10 cattle to request that she be married to them," the Times of Swaziland newspaper quoted a Swazi palace source as saying, referring to a customary meeting between families before a marriage.
No wedding date has been set, it said.
Zuma's spokesperson, Lakela Kaunda, confirmed that the deputy president would marry Dlamini, but said she had nothing to add.
The deputy president has been married three times. He is divorced from Foreign Minister Nkosazana Dlamini-Zuma. His wife Kate died of heart failure in 2000, and he is still married to a third woman, Sizakele.
Polygamy is common in Swaziland, a tiny landlocked kingdom.
In neighbouring South Africa, if a marriage by customary union is not registered with the authorities, a man is permitted to have more than one wife. If a marriage is registered by so-called Christian rites, then only one wife is allowed.
Dlamini, a police officer, is the daughter of the king's brother Prince Phiwokwakhe Dlamini - a palace-appointed member of parliament.