The 37-year-old was proclaimed head of an army junta after rebels killed his father Idriss Deby Itno, who had seized power in a coup and ruled the desert nation with an iron fist for three decades.
Mahamat Deby Itno had promised to hand power back to civilians and organize elections within 18 months but added another two years of transition.
The end of the transition period was pushed back to October 10 this year.
"Beyond this date, the country will fall into a legal void, synonymous with foreseeable chaos," Ahmet Bartchiret, president of the ANGE electoral commission said Tuesday.
"It is therefore imperative to hold the elections before," he explained while announcing the date.
In mid-January, the ruling Patriotic Salvation Movement (MPS) party designated Mahamat Deby Itno as its candidate for the presidential election.
Mahamat Deby Itno had told the African Union he would not run for president, but a new constitution adopted by a mid-December referendum allows him to do so.
The Chadian opposition has asked the president not to run for a new term.
The leading opposition and civil society grouping Wakit Tamma has accused the international community, and former colonial ruler France in particular, of supporting "dynastic succession" and backing Mahamat Deby Itno's "ambition to confiscate power, including by the use of force."
In October 2022, between 100 and 300 young men peacefully demonstrating against the extension of the transitional government were shot dead in the Chadian capital N'Djamena by security forces, according to the opposition and NGOs.
More than 1,000 others were imprisoned before being pardoned, while dozens more were tortured or have disappeared, the same sources said.
In the aftermath of the massacre Amnesty International notably decried a lack of "serious investigation" into the killings and who was responsible.
At the end of December 2023 a new constitution was adopted after a referendum produced an 86% vote in favor, despite the opposition boycott.
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