Hainau may refer to:

• Chojnów, Poland, Hainau in German
• Hainau, Germany, in Rhein-Lahn-Kreis, Rhineland-Palatinate

• Gai choy
• Gaicht Pass
• GAIC JJ-7
• Gaida
• Gaidal Cain
• Gaidamak
• Gaidar
• Gaidar Aliev
• Gaidar Gadzhiyev
• Gaiden Shinji
• Gaideris of Benevento
• Gai dimanche
• Gaidojutsu
• Gaidropsarus vulgaris
• GAIE
• Gai Eaton
• Gaiemmae Station
• Gaienhofen
• Gaiety Theatre
• Gaiety Theatre (disambiguation)
• Gaiety Theatre, Isle of Man
• Gaiety Theatre, London
• Gaiety Theatre, New York (male burlesque)
• Gaigan
• GAIGC JL-9/FTC-2000