|• Mayor (2020–2026)||Gaëlle Nicolas|
|20.81 km2 (8.03 sq mi)|
|• Density||250/km2 (640/sq mi)|
|Time zone||UTC+01:00 (CET)|
|• Summer (DST)||UTC+02:00 (CEST)|
|Elevation||2–206 m (6.6–675.9 ft)|
|1 French Land Register data, which excludes lakes, ponds, glaciers > 1 km2 (0.386 sq mi or 247 acres) and river estuaries.|
Châteaulin is in a valley towards the center of Finistère on the River Aulne and the Canal de Nantes à Brest, mid-way between Quimper to the south and Brest to the north. To the west the Menez-Hom hills separate it from the Crozon peninsula and the Bay of Douarnenez, which opens into the Atlantic Ocean.
In French the inhabitants of Châteaulin are known as Châteaulinois.
|Source: EHESS and INSEE (1968-2017)|
In 2008 1.96% of primary-school children attended bilingual schools.
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.
- Yves Marie André, better known as le Père André (1675–1764), Jesuit priest and philosopher.
- 27 November 1761 : Birth of Julien Marie Cosmao-Kerjulien (died in Brest 17 February 1825), Rear-Admiral and Baron d'Empire.
- Jean Moulin, emblem of the French Resistance during the Second World War, was the sub-prefect from 1930 to 1933.
- Henri Ernest Ponthier de Chamaillard, usually known as Ernest de Chamaillard, (9 December 1862, Gourlizon – 1931, Eaubonne) was a French artist, one of a group of painters who gathered in the Breton village of Pont-Aven. He was a friend and student of Paul Gauguin. In 1893, unable to make a living from his painting, he moved to Châteaulin behind Église Saint-Idunet where he worked as a lawyer until 1905.
Châteaulin is twinned with:
- Cantons of the Finistère department
- Communes of the Finistère department
- Arrondissements of the Finistère department
- Parc naturel régional d'Armorique
- "Répertoire national des élus: les maires". data.gouv.fr, Plateforme ouverte des données publiques françaises (in French). 2 December 2020.
- "Populations légales 2020". The National Institute of Statistics and Economic Studies. 29 December 2022.
- Des villages de Cassini aux communes d'aujourd'hui: Commune data sheet Châteaulin, EHESS (in French).
- Population en historique depuis 1968, INSEE
- (in French) Ofis ar Brezhoneg: Enseignement bilingue
- Official website of the town of Châteaulin / Kastellin (in French)
- Base Mérimée: Search for heritage in the commune, Ministère français de la Culture. (in French)