Gau (plural Gaue, Dutch: gouw, Frisian: gea or goa) is a Germanic term for a region within a country, often a former or actual province. It was used in medieval times, when it can be seen as roughly corresponding to an English shire. The administrative use of the term was revived as a subdivision during the period of Nazi Germany in 1933–1945. It still appears today in regional names, such as the Ambergau.

A Gäu landscape (Gäulandschaft) refers to an area of open, level countryside in the south German language (Alemannic area, or in Switzerland). These regions typically have fertile soils resulting from depositions of loess (an exception is the Arme Gäue ("Poor Gäus" of the Baden-Württemberg Gäu).