France

Castelnau or Castelnaud (castel 'castle' and nau 'new' in Occitan) is part of the name of several communes in the south of France:

• Castelnau-Barbarens, in the Gers département
• Castelnau-Chalosse, in the Landes département
• Castelnau-d'Anglès, in the Gers département
• Castelnau-d'Arbieu, in the Gers département
• Castelnau-d'Aude, in the Aude département
• Castelnau-d'Auzan, in the Gers département
• Castelnau-d'Estrétefonds, in the Haute-Garonne département
• Castelnau-de-Brassac, in the Tarn département
• Castelnau-de-Guers, in the Hérault département
• Castelnau-de-Lévis, in the Tarn département
• Castelnau-de-Mandailles, in the Aveyron département
• Castelnau-de-Médoc, in the Gironde département
• Castelnau-de-Montmiral, in the Tarn département
• Castelnau-Durban, in the Ariège département
• Castelnau-le-Lez, in the Hérault département
• Castelnau-Magnoac, in the Hautes-Pyrénées département
• Castelnau-Montratier, commune in the Lot département
• Castelnau-Montratier (delegated commune), delegated commune in the Lot département
• Castelnau-Pégayrols, in the Aveyron département
• Castelnau-Picampeau, in the Haute-Garonne département
• Castelnau-Rivière-Basse, in the Hautes-Pyrénées département
• Castelnau-sur-Gupie, in the Lot-et-Garonne département
• Castelnau-sur-l'Auvignon, in the Gers département
• Castelnau-Tursan, in the Landes département
• Castelnau-Valence, in the Gard département
• Castelnaud-de-Gratecambe, in the Lot-et-Garonne département
• Castelnaud-la-Chapelle, in the Dordogne département
• Saint-Michel-de-Castelnau, in the Gironde département

England

• Castelnau, London, an estate and road in Barnes, south-west London

Canada

• De Castelnau station, a Montreal Metro station in the Villeray–Saint-Michel–Parc-Extension borough
• Castelnau Lake, a freshwater body of the catchment area of the rivière à la Chasse in Baie-Comeau, Quebec