Groß-Gerau is a Kreis (district) in the south of Hesse (Hessen in German), Germany.

Starting in 1066 the counts of Katzenelnbogen became the rulers of the area, until in 1479 it came to Hesse.

The highest elevation of the district is 145 m above sea level, located near Mörfelden on a former garbage deposit, the lowest is 83.2 m high and situated at the mouth of the Main into the Rhine.

The dexter (armsbearer's right, viewer's left) side of the coat of arms shows bars in the red and silver tinctures of Hesse, the sinister (armsbearer's left, viewer's right) side the silver and black bars of the Counts of Isenburg.

In the middle are the arms of the Von Dornberg family, the ancestors of the Counts of Katzenelnbogen.