Bahia ya Masr, a movement that promotes citizenship rights, has called on Egyptian women to protest against the draft constitution on Wednesday at 5pm in front of the Nahdet Masr statue at Cairo University in Giza.
The demonstrators will "reject the illegitimate referendum" and demand "freedom, justice, and dignity" for all citizens, the group said via Facebook.
The protest will also call for women's rights to be protected and promoted.
The first phase of Egypt's referendum took place on 15 December across 10 governorates.
Unofficial results of the first round show 56.5 per cent approval for the draft charter, while 'No' votes reached 43.5 per cent.
The second phase of voting includes the remaining 17 governorates and will take place on 22 December.