Prince Sultan passed away while visiting the United States for medical diagnostic testing, CNN reported, citing a US State Department official on Saturday.
Bin Abdul Aziz had served as the defense minister for the Saudi kingdom over the past five decades.
In July, the ailing Saudi crown prince underwent an operation in a New York hospital.
He had been receiving medical treatment for the last two years.
The nature of his illness had never been officially revealed, although analysts and diplomats believed it was cancer.
The Saudi crown prince, who was the half-brother of King Abdullah, had spent several lengthy stays outside Saudi Arabia in recent years.
Prince Nayef, Sultan’s full brother, has also received unspecified treatment during the past 20 months. Now in his mid-70s, Nayef has served as the Saudi interior minister for 35 years