Don Mot Daeng (, ; , ) is a district (amphoe) in the central part of Ubon Ratchathani province, northeastern Thailand. The district is named after the island Don Mot Daeng in the Mun River.
The area of the district was split off from Mueang Ubon Ratchathani district and formed a minor district (king amphoe) on 1 April 1991. It was upgraded to a full district on 5 December 1996.
The name Don Mot Daeng means "upland of red ant".
Neighboring districts are (from the east clockwise): Tan Sum, Sawang Wirawong, Mueang Ubon Ratchathani, Lao Suea Kok and Trakan Phuet Phon of Ubon Ratchathani Province.
The important water resources are the Mun and Se Bok River.
The district is divided into four sub-districts (tambons), which are further subdivided into 46 villages (mubans). There are no municipal (thesaban) areas, and four tambon administrative organizations (TAO).