The crowds came out as a show of angst against the ruling military and a show of support to Mursi, who as president elect is negotiating with the Army the powers his civilian administration will wield.
People started arriving at Tahrir right from the early morning hours to take part in a million people march against the recent orders to dissolve the elected parliament and a constitutional addendum that gives the ruling military council new powers at the expense of the elected president.
Mursi, who is scheduled to take oath tomorrow morning, will address the people today at the Square, that was the centre of last year's historic revolution.
While the crowds kept growing by the hour, Mursi offered Friday prayers at the Al-Azhar mosque before heading to the Tahrir to deliver a major speech to the nation, Al Ahram said.
In the absence of a parliament, the president-elect will take oath in front of the Constitutional Court, another issue that has caused resentment among the people.
Today's protest under the slogan 'Handover Power', has been called by a group of revolution activists who led last year's uprising.
Essam El-Erian, vice-president of the Muslim Brotherhood's Freedom and Justice Party (FJP), said the party would maintain a sit-in at the Tahrir until executive power was handed over to the democratically-elected leader by the Supreme Council of the Armed Forces (SCAF).
While Egyptians have voted over a year after an uprising that ousted Hosni Mubarak, many feel the results of the revolution are yet to be consolidated into a civilian rule, as the ruling military appears increasingly reluctant to complete the transition of power. PTI