Châteaulin (French: [ʃɑtolɛ̃] ⓘ; Breton: Kastellin) is a commune in the Finistère department and administrative region of Brittany in north-western France.

To the west the Menez-Hom hills separate it from the Crozon peninsula and the Bay of Douarnenez, which opens into the Atlantic Ocean.

[5] Châteaulin's economy is based on food processing (salmon and poultry) and, to an ever-greater extent, tourism.

The Gendarmerie school on the outskirts of the town provides for a large number of families and the many recruits passing through the school provide the economic backbone of the town's night-life.

The cake shop Histoire de Macaron is famous for its tasty and wide range of macaroons as well as the Java, created in 1907 by Mister Le Meur, which is a legend in the town.