Chileans rejected on Sunday a new constitution that would have replaced the charter drawn up during Gen. Augusto Pinochet's dictatorship in 1980.
With counting nearly complete, the rejection camp has 62% of votes compared to 38% in favor of approval.
The drafting of the new constitution began in 2019 after massive protests resulted in a first plebiscite where 80% of the population supported the move.
Over 12 months, 155 elected individuals, representing a variety of voices, worked to draft the new constitution.
The result, presented to President Gabriel Boric in July, was a 178-page progressive document that embodies gender equality and Indigenous rights, expands social protections and prioritizes the environment.
While the rejection was expected as latest polls suggested 58% would vote against the document, the margin for the rejection camp was wider than anticipated.
The result represents a defeat for Boric, who presented the new constitution as a solution to the social and political tensions in Chile.
In a bid to assuage the fears of the undecided, the president had proposed changes even if the constitution was approved.
"The Chilean people were not satisfied with the proposed constitution and, therefore, have decided to reject it clearly at the ballot box," Boric said in a televised message on Sunday.
"Those of us who have historically been supporters of this transformation process must be self-critical," he added.
The president summoned all parties on Monday to give continuity to the "constituent process."
Voting was mandatory for more than 15 million citizens in the South American country of some 19 million people.
After Sunday's results, the current constitution will remain in effect and the government is expected to begin a new constitutional process.
