Dexheim (German pronunciation: [ˈdɛkshaɪm]) is an Ortsgemeinde – a municipality belonging to a Verbandsgemeinde, a kind of collective municipality – in the Mainz-Bingen district in Rhineland-Palatinate, Germany.

Dexheim lies between Mainz and Worms, in Rhenish Hesse. The winemaking centre belongs to the Verbandsgemeinde Rhein-Selz, whose seat is in Oppenheim.

Dexheim's history began long before its first documentary mention. Finds within Dexheim's municipal limits have yielded information about the Germani who lived here. These artefacts can be seen at the Roman-Germanic Central Museum (Römisch-Germanisches Zentralmuseum) in Mainz. When the Romans needed bricks to build their castra, they took as their raw material the loam from Dexheim to shape and fire into bricks.

In 774 Dexheim had its first documentary mention in a donation document in which Charlemagne bequeathed a great estate to the Lorsch Abbey. The second documentary mention is contained in an act in which King Arnulf of Carinthia donated the church at Dexheim to the Fulda Abbey.

Dexheim was a Free Imperial Village, paying taxes only to the Emperor. Its coat of arms was a silver cross with the red “Imperial Apple”. With the neighbouring places of Nierstein and Schwabsburg it became the site of the common court. In 1376 it passed to the Oberamt of Oppenheim and remained with it until the Electorate of the Palatinate was no more.

Until then the village had already had many landlords. For lack of money – something similar had already happened earlier – the Emperor had pledged Dexheim in 1315 to the Archbishop of Mainz, redeeming it in 1353.

The Thirty Years' War was frightful for Dexheim. A document from 1647, and thus one year before the Peace of Westphalia, gives an impression. Almost all the houses were destroyed; only the palace of the Lords of Dienheim and a few houses nearby were habitable.

Dexheim's importance is also underscored by the names of noble families that had holdings here. Found here, among others, are names such as: