Diffa is a city and Urban Commune in the extreme southeast of Niger, near that country's border with Nigeria. It is the administrative seat of both Diffa Region, and the smaller Diffa Department. As of 2011, the commune had a total population of 48,005 people.
Diffa marks the eastern end of the paved section of Route Nationale 1, the main east west highway across Niger, although the section between Zinder and Diffa is only partially paved in places. RN 1 continues north to N'guigmi more than 100 km. Maïné-Soroa, the other major town of the Region, lies less than 100 km to the west of Diffa. The border with Nigeria, at the Nigerian town of Duji, is 5.5 km to the south of Diffa. Diffa Airport lies to the north of the town.