Ouaddaï or Wadai (Arabic: وداي) is a region of Chad, located in the south-east of the country, with its capital at Abéché.

Both capitals of the Empire - Ouara (now uninhabited) and Abéché - are located in modern Ouaddaï region.

The terrain is generally flat savannah, rising slightly towards the east where the Ouaddaï highlands are located.

Abéché is the capital of the region and is the fourth largest city in Chad; other major settlements include Abdi, Adré, Am Hitan, Bourtail, Chokoyan, Hadjer Hadid, Marfa, Mabrone and Tourane.

[1] The main ethnolinguistic groups are the Assangori, Baggara (generally speakers of Chadian Arabic), Dar Sila Daju, Kajakse, Karanga, Kendeje, Maba (including the Marfa sub-group), Mararit, Masalit and Surbakhal.