Castelnaudary (French: [kastɛlnodɑʁi] ⓘ; Occitan: Castèlnòu d'Arri) is a commune in the Aude department in the Occitanie region of southern France.

Castelnaudary is the main port of the Canal du Midi to which it owed a period of prosperity in the 17th century when agricultural and manufactured produce became easier to export.

The Grand Bassin in the town is at 7 ha the largest open area of water in the canal, and is today its major pleasure port.

[3] Castelnaudary comes from the Occitan Castèlnòu d'Arri — Latin translation Castellum Novum Arri — meaning "Arrius' new castle".

The cassoulet variant favored in this town is based on the local haricot bean (which is the subject of a protected status application).