Egypt's Prosecutor General Hesham Barakat succumbed to injuries he sustained earlier on Monday in a bomb attack in Cairo, official MENA news agency reported.
Barakat, 65, was seriously wounded and taken to a hospital in Cairo where, despite undergoing emergency surgery, he breathed his last.
The health ministry said nine other people were injured in the blast that targeted the country's top prosecutor.
The bombing came after Sinai-based Ansar Bayt al-Maqdis militant group, an affiliate of the Islamic State regional militant group, posted a video clip on Monday purportedly showing attacks in May that killed two judges and a prosecutor.
The group has vowed more attacks on judges in revenge for mass life and death sentences handed down to Islamists.
Barakat has referred thousands of Islamists to mass trials in criminal courts over violence charges since the ouster of Islamist President Mohamed Morsi in July 2013.
