Debuchy is surplus to requirements at Arsenal and was left out of the squad which travelled to Australia and China for pre-season training.
The 31-year-old’s career at the Emirates has faltered badly since he arrived in 2014 from Newcastle.
In his debut season, Debuchy suffered an ankle injury and then dislocated his shoulder a month later.
The emergence of Hector Bellerin also meant the France international was unable to regain his place in the starting XI.
Arsenal stars enjoy training in Shanghai Mon, July 17, 2017
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Debuchy is likely to be the first of several players to leave Arsenal this summer
Last season Debuchy made just one appearance in all competitions for Arsenal and with Arsene Wenger looking to trim his squad, the right-back is on his way out.
And according to French outlet RMC Sport, Debuchy will attempt to kickstart his career again at Nice.
He is expected to undergo a medical and complete his move by the end of the week.
Mathieu Debuchy is on his way back to France
Nice finished third in Ligue 1 last term and qualified for the Champions League third qualifying round.
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Debuchy is likely to be the first of several first team players to leave Arsenal this summer.
Lucas Perez, Kieran Gibbs and Carl Jenkinson were also left behind to seal transfer away from the club.