Mohamed Morsi, the Egyptian president, has signed into law the new constitution, saying that it will help end political turmoil and allow him to focus on fixing the fragile economy.
The presidency said Morsi signed a decree enforcing the charter late on Tuesday after the official announcement of the result of a referendum approving the basic law, Egypt's first constitution since toppling of former President Hosni Mubarak's overthrow.
Meanwhile, country's Shura Council, or upper house of parliament, is holding its first session since the country approved the new constitution.
Morsi is expected to address the Shura Council on Saturday, which is is expected to draft a law regulating
upcoming parliamentary elections in about two months.
The text of the constitution has sharpened painful divisions in the Arab world's most populous nation and prompted protests on the streets of Cairo.
Opposition groups condemn the new basic law as too Islamist and undemocratic, saying it could allow clerics to intervene in the lawmaking process and leave minority groups without proper legal protection.
Results announced on Tuesday, which followed two rounds of votes, showed Egyptians had approved the text with an overwhelming 63.8 percent.
The National Salvation Front (NSF), Egypt's main opposition coalition, alleged that there were a few incidents of fraud during the vote.
But Judge Samir Abou el-Maati, the head of the electoral commission, denied allegations that judicial supervision was lacking in the vote.
The win gives Islamists their third straight electoral victory since former President Hosni Mubarak was toppled in a 2011 revolution, after their earlier wins in parliamentary and presidential elections.
Muslim Brotherhood leader, Mohamed Badie, tweeted: "Congratulations to the Egyptian people on approving the constitution of revolutionary Egypt. Let's start building our country's rebirth... men and women, Muslims and Christians."
Morsi believes adopting the text is key to ending a protracted period of turmoil and uncertainty that has wrecked the economy.
He has argued that the constitution offers enough protection to all groups, saying many Egyptians are fed up with street protests that have prevented a return to normality and distracted the government from focusing on the economy.
But the opposition has argued that the Muslim Brotherhood and Salafist groups want to use some of the charter's ambiguous language to slip in sharia-style strict Islamic law.
Front leader Mohamed ElBaradei, a Nobel Peace laureate and former chief of the UN atomic energy agency, has said the new charter should be treated as an "interim one" until another is written up on the basis of consensus.
The US, which provides billions of dollars a year in military aid to Egypt, has called on Egyptian politicians to bridge divisions and on all sides to reject violence.
"President Morsi, as the democratically elected leader of Egypt, has a special responsibility to move forward in a way that recognises the urgent need to bridge divisions," acting State Department spokesman Patrick Ventrell said in a statement.
EU foreign policy chief Catherine Ashton took note of both the majority backing the constitution and the low turnout.
Repeating a call for dialogue, she added: "I urge those concerned, in particular the president, to intensify efforts in this regard."