More than 1,400 delegates from the military government, civil society, opposition parties, trade unions and rebel groups gathered in N'djamena for the talks that are scheduled to last three weeks.
Delayed talks on Chad's future that the ruling junta says are a "decisive moment" have opened, even as some opposition groups boycott the gathering.
Junta chief General Mahamat Idriss Deby described the forum on Saturday as a "decisive moment in history of our country" after arriving in military dress surrounded by tight security to open the forum.
Earlier, he had first inaugurated a statue symbolising national unity at the January 15 palace in the capital N'djamena before reviewing an honour guard, an AFP journalist at the scene saw.
"This dialogue should allow us definitively to put recourse to arms behind us," said government spokesperson Abderamane Koulamallah.
Deby in midweek signed a decree saying the forum would make "sovereign" decisions which would be legally binding and that he would act as guarantor.
The junta head took power in April 2021 at the age of just 37 after his father, who ruled for 30 years, was killed during a military operation against rebels.
READ MORE: Chad 'national dialogue' set to kick off after delays
Lasting peace, reforms top agenda
Deby says the talks should open the way to "free and democratic" elections after an 18-month rule by the junta — a deadline that France, the African Union (AU) and others have urged him to uphold.
The dialogue, which should have begun in February, was hit by repeated delays as Chad's numerous rebel groups, meeting in Qatar, squabbled over whether to attend.
In the end, around 40 groups on August 8 signed up to a deal that included a ceasefire and guarantee of safe passage.
How to achieve lasting peace, reform state institutions and grant fundamental freedoms to all topped the agenda.
Committees must also draw up a new constitution that will be put to a referendum.
While a number of opposition groups appeared ready to give the forum a chance, some groups did not attend.
The Front for Change and Concord in Chad (FACT) boycotted the event which it considers to be "skewed in advance" towards the military junta.
FACT is a key opposition group which did not sign the peace accord and which triggered the offensive in the northeast last year that ended in the death in combat of Deby's father Idriss Deby.
READ MORE: Chad military leader signs accord to launch peace talks with opposition