No other details about his death were immediately available, but arrangements are under way to transport his body back to Saudi Arabia, officials said.
Crown Prince Sultan, thought to be in his 80s, was Saudi Arabia's minister of defense, and was one of the top figures in the Saudi kingdom. He's had various medical issues in recent years. In 2009, he was in New York for surgery for an undisclosed illness and had also flown to Morocco for medical treatment over the years.
The country's royal court released a statement about the death Saturday. "King Abdullah bin Abdulaziz Al-Saud mourns the death of his brother and his Crown Prince ... Prince Sultan bin Abdulaziz Al-Saud," the statement said.
The statement also said he died "outside the kingdom following an illness," but did not release details on the ailment. Reports in recent years have indicated that Crown Prince Sultan was battling cancer.
King Abdullah's half-brother was the desert kingdom's defense minister for decades, meeting regularly with visiting dignitaries. He took a leading role in Saudi Arabia's involvement in the 1991 Gulf War against Iraq, heading a coalition of about half a million troops from more than 30 countries.
Of his many children, perhaps the best known internationally is Prince Bandar bin Sultan bin Abdulaziz Al-Saud, Saudi Arabia's former ambassador to the United States. Prince Bandar served as ambassador from 1983 to 2005 and was friends with the family of President George W. Bush.
Saleh Al-Namla, a member of Saudi Arabia's Shura Council, said the prince would be missed. "Crown Prince Sultan lived his life in service of his country and also serving the Arab people and the people of Saudi Arabia," Al-Namla, said. "He was very much loved by the country."
Prince Sultan's death brings up questions about who will now be named crown prince. Many have felt that Prince Nayef bin Abdulaziz Al-Saud would be the one to get that post. In 2009, King Abdullah appointed Prince Nayef as the country's second deputy prime minister as rumors started to circulate about Prince Sultan's failing health.
At the time many Saudis took the appointment to mean that Prince Nayef was made the country's crown prince in the place of the ailing Sultan and was second in line to be king, King Abdullah in 2007 created a group called the Allegiance Council to make decisions on succession issues. It is unclear when this group, made up of members of the royal family, will make a decision on who will be named the crown prince.