Diffa gari ne, da ke a yankin Diffa, a ƙasar Nijar. Shi ne babban birnin yankin Diffa. Bisa ga ƙidayar jama'a a shekarar 2011, jimilar mutane 48,005 (dubu arba'in da takwas da biyar). Hukumar Kididdiga ta Nijar wato INS ta yi kiyasin cewar yawan jama'ar Diffa sun kai kimanin dubu sittin da biyar (65 000) a shekarar 2017. Birnin Diffa yana a Kudu maso gabashin Nijar kuma tana da iyaka da Bornon Najeriya. Birnin Diffa ya samu asali tun lokacin Daular Borno wato tun lokacin 1900. Asalin mutanen da sukayi rayuwa cikinta Kanuri (ko kuma barebari) ne. Amma a yau akwai Larabawa, Tubawa da kuma Buzaye masu rayuwa a cikin ta. Tun bullowar rikicin Boko Haram a shekarar 2010 Birnin Diffa ya cika da baki en gudun hijira wadanda suka fito daga makwabciya Najeriya. Ft Diffa tana a arewacin kogin Komadugu Yobe. Diffa na nesa na kimanin kilometa 1360 daga babban birnin Niamey.