Bafokeng king Kgosi Lebone Molotlegi II died of a heart attack on Wednesday, the Bafokeng royal family announced.
Molotlegi was 35 years old.
Kgosi Lebone Mollwane Boikanyo Molotlegi was to have been enthroned in September this year after succeeding his father, Lebone I who died in 1995.
The family said in a statement Molotlegi fell ill during a holiday in New York in February, forcing him to cut short his visit, and was admitted to hospital on his return home.
On March 5 he was admitted to Morningside Clinic.