The Réseau Breton (RB) is a 1,435 mm, standard gauge, and former 1,000 mm, metre gauge, railway in Finistère, France, with a few kilometres of line in Côtes d'Armor, Ille-et-Vilaine and Morbihan. The hub of the system was Carhaix. The metre gauge lines were built with the capacity to be easily converted to standard gauge if necessary.

The Chemins de fer départementaux du Finistère were a metre gauge railway system in northwest Brittany, France. It was opened in stages between 1893 and 1907, and closed in 1946. The system had a total extent of 214 kilometres (133 mi).