After lambasting critics of his intervention, he said: "We want to correct the paths of the revolution and history."
In September Saied ignored most of the 2014 democratic constitution to say he would rule by decree during a period of exceptional measures, promised dialogue for further changes.
While critics say it was a coup, the president defends the move as the only way to end governmental paralysis after years of political stagnation and economic stagnation, compounded by the pandemic.
In September Saeid named Najla Bouden Romdhane, a university engineer who worked with the World Bank, as the country's first female prime minister, just two months after dismissing Prime Minister Hichem Mechichi.
Saied, a sharp critic of the North African country's 2014 constitution, said the nationwide public consultation would take place from January 1 until March 20, gathering constitutional and related reform suggestions.
Saied similarly announced he would appoint an expert committee to draft a new constitution, which will be ready by June before the referendum.
������Tunisian President Kais Saied has prolonged the suspension of parliament and announced a national referendum, almost five months after dismissing his government and granting himself sweeping powers#Tunisiahttps://t.co/49QzJXmI4t
Earlier on Monday, Saied had told the cabinet that constitutions are "not eternal." "The people exercises its sovereignty in the framework of the constitution," Saied said.
"So if it's not possible for the sovereign people to practise its rights in the framework of a text, then there needs to be a new text."
The 2014 constitution created a hybrid presidential-parliamentary system, though many Tunisians see the political system it created as having failed, with increased corruption and endless blockages and no resolution of profound social and economic problems.
Tunisians, who have blamed the political class for doing little to create jobs and raise the living standard, largely cheered on Saeid's announcement.
Parliament Speaker Rached Ghannouchi alleged President Saied was launching "a coup against the revolution and constitution" after the July move, which critics stated was a major setback to the democratic advances won in the 2011 revolution.
Ghannouchi leads the Islamist Ennahdha party, which currently dominates the now-suspended Parliament.