The Alsatian Nordgau was a medieval Gau in an area roughly comparable to the present-day French Bas-Rhin department.
In the Middle Ages, what was then Alsace was divided into two districts, called Nordgau (“Nordgowe”, Unterelsass) and Südgau (“Suntgowe”, Sundgau, Oberelsass).
The family developed into the Counts of Egisheim and Dagsburg, whose possessions were however situated more in Upper Alsace.
The last Count was Hugues VII de Dabo who was dispossessed of Nordgau by Henry IV, Holy Roman Emperor, during the Investiture Controversy, and killed in 1089 in an attempt of its recover.
The Nordgau was later largely merged into the Prince-Bishopric of Strasbourg, other parts came to the Habsburgs and the Décapole.