The inauguration comes a day before the anniversary of some of the fiercest confrontations between protesters and security forces on a street adjoining Tahrir Square, in which at least 45 people were killed by police in 2011.
Some of those who participated in those popular revolts feel the memorial doesn't honor the dead as much as it tries to paper over the continuing deep disputes over Egypt's future.
The day is expected to bring new rallies and, it is feared, new unrest.
Activists were quick to point out the bitter irony of the government erecting a memorial to the "martyrs," when there is no effort to prosecute police or military officials over their deaths and there is less official tolerance for protests.
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Soldiers routinely block the often-deserted square with armored personnel carriers and barbed wire on days authorities fear protests and clashes could reach the central Cairo plaza.
Tahrir has been the symbolic heart of protest throughout more than two and a half years of Arab Spring revolt in the country. First, it was the main stage for the 18 days of protests that ousted autocrat Hosni Mubarak in February 2011.
Then it was the scene of frequent protests by opponents of the military, which took over direct power after Mubarak's fall repeatedly leading to deadly clashes with the police and troops.
Since then, supporters of the military and the new interim government have effectively claimed control of the square.