Gau may refer to:
- Gau, a Cantonese vulgar word
- GAU, the University of Göttingen (German: Georg-August-Universität Göttingen)
- Gau (country subdivision), German term for a shire (regional administration)
- Gau (grape), another name for the French wine grape Gouais blanc
- Gau, a character in Final Fantasy VI
- Gau Meguro, a character in the manga Nabari no Ou
- Gau Island, an island in Fiji
- Gau Mata, a sacred cow in Hinduism
- General Assistance Unemployable a Washington State unemployment program
- Lokpriya Gopinath Bordoloi International Airport in Guwahati, Assam, India (IATA code GAU)
- Saint Gaugericus (Gau, Géry)
- Gäu District, district of Solothurn, Switzerland
- Girne American University, a university in Northern Cyprus
- Gun, aircraft unit, a series of US aircraft guns:
- Minigun, also known as GAU-2/a or GAU-17/A
- M61 Vulcan, also known as GAU-4/A
- GAU-7 cannon
- GAU-8 Avenger
- M2 Browning machine gun, different versions known as GAU-10/A, GAU-15/A, GAU-16/A, GAU-18/A or GAU-21/A
- GAU-12 Equalizer
- GAU, Größter Anzunehmender Unfall ("maximum credible accident"), German term used for nuclear accidents at approximately level 4 on the International Nuclear Event Scale, accidents that reactors are planned to withstands
- Super-GAU, beyond design basis accidents, such as the Chernobyl and Fukushima-I disasters
People with the surname Gau:
- Franz Christian Gau (born 1790), German architect and archæologist.
- Andreas Gau (born 1800), German theologist.
- Walter Gau (born 1956), Austrian politician.
- Sebastian Gau (born 1983), German football player.