Dieburg () is a small city in southern Hesse, Germany. It was the seat of the district ("Kreis") of Dieburg until 1977, when it became part of the new district of Darmstadt-Dieburg.
Early mentions of Dieburg date back to the early 13th century, with various spellings of its name attested. The city's name is derived from the Middle High German words , meaning "people", and , meaning "castle". Therefore, Dieburg refers to the castle of the people, located in the centre of the medieval town. The town's centre largely consists of historical timber-framed houses from medieval times. The Dieburg Museum, located in the Fechenbach stately home, displays archeological findings. Of special interest is a Roman temple relief of Mithras and a dyer's workshop. The coat of arms of the town Dieburg shows Martin of Tours. A cultural highlight is the yearly carnival, including a carnival parade that is completely based on honorary posts.
Dieburg is situated north of mountain range Odenwald in southern Hesse. The Gersprenz (47 km), tributary to the Main, flows through Dieburg. The city of Darmstadt is located 15 kilometres to the West, the city of Frankfurt on the Main is located around 40 kilometres to the North of Dieburg.
Dieburg is twinned with: