Egyptians are voting for a third and final day on constitutional amendments that would allow President Abdel-Fattah el-Sissi to remain in office until 2030.
The referendum is virtually guaranteed to be approved, as the government pushes for high turnout to grant it legitimacy.
Authorities have waged a wide-scale crackdown on dissent since el-Sissi led the military overthrow of an elected but divisive Islamist president in 2013. The referendum is widely seen as another step toward restoring authoritarian rule eight years after a pro-democracy uprising.
Opposition parties have called on voters to reject the measure, but they have little influence in parliament, which is packed with el-Sissi supporters and overwhelmingly approved the changes.
Polls reopened at 09:00 (0700 GMT) on Monday. The results are expected within a week.