Darmstadt-Dieburg is a Kreis (district) in the south of Hesse, Germany.

Neighboring districts are Offenbach, Aschaffenburg, Miltenberg, Odenwaldkreis, Bergstraße, Groß-Gerau, and the district-free city of Darmstadt, which it surrounds.

Most famous in the district is the Messel Pit, where many fossils in the oil shale of a Tertiary lake were found.

Both owned big parts of the districts area in the past.

The 23 stars in the bottom represent the municipalities of the county.