He was about 79 years old. Critics denounced him as a repressive opponent of civil rights and minorities in the kingdom, while admirers said he was a warmer man and a more reform-minded leader than he was given credit for.
Crown Prince Nayef's legacy would be as "police chief" to his country for more than five decades, said British historian Robert Lacey, who has chronicled the Saudi ruling family since the 1980s.
Prince Nayef, who had served since the 1970s as deputy interior minister and then interior minister, came close to succeeding to the Saudi monarchy only in his late 70s, when his half-brother King Abdullah appointed him crown prince and most-likely heir in October 2011.
Prince Nayef's time as crown prince served as a postscript to a career otherwise devoted to the country's internal security. In his short spell as heir to the throne, he surprised many Saudis by ushering in modernizations, including removing religious authorities who objected to the mingling of men and women in public spaces.