Sheikh Mohammed Sayed Tantawi, Sunni Islam's most senior religious figure, has died during a visit to Saudi Arabia.
The 82-year-old Egyptian, who had previously undergone heart surgery, suffered a heart attack as he boarded a flight early Wednesday morning, Egyptian television said.
He was admitted to the Amir Sultan hospital in Riyadh where doctors proclaimed him dead.
Tantawi - who headed al-Azhar, Sunni Islam's highest seat of learning - was known for his controversial ban of the niqab, which he said had no basis in Islam.
He also wrote a number of books, including a 15-volume, 7,000-page encyclopedia on the interpretation of Quran.
His body is likely to be sent back to Cairo on Wednesday evening, local television said.