Tunisian President ratified a that will give him unchecked powers during a at the presidential palace on Wednesday.
After signing the document, Saied said the constitution "corrected the course of the revolution and the course of history" following a period of "darkness" and "injustice" for Tunisia.
A new electoral law will be drafted and a constitutional court established soon "to preserve the constitution, and to protect the rights and freedoms that come with the new constitution", he added.
Tunisia held a referendum for a new constitution on 25 July, a year after Saied sacked the Tunisian government and suspended parliament in .
The president and his supporters said the political system had to change to save Tunisia from years of stagnation and political paralysis.
But opponents have said the new constitution tips Tunisia back into the dictatorship it had before the revolution of 2011.
The constitution places the president in command of the army, allows him to appoint a government without parliamentary approval, and makes him virtually impossible to remove from office.
Tunisia's electoral commission announced final results for the referendum on Tuesday, showing 94.6 percent of votes in favour and a 30.5 percent voter turnout.
Opposition groups had called on Tunisians to boycott the referendum and this was the lowest ever turnout for a Tunisian poll since the 2011 revolution.