City walls of Dinan, Medieval ramparts in Dinan, France

The city walls of Dinan are a medieval fortification system that extends several kilometers around the historic core, equipped with defensive towers and monumental gateways. The walls are constructed from cut stone blocks and remain largely intact, though some sections show repairs and modifications made over later centuries.

The walls were built from the 13th century by the lords of the Dinan family; no contemporary document survives, so the exact start cannot be dated. In 1265 Duke Jean I le Roux bought the seigneury of Dinan and Léhon for 16,000 livres from Alain II d'Avaugour, a sale contested by Henri I until the Paris court ruled in 1283. Under the dukes, three gates, many towers and a keep rose in the early 14th century; from 1476 to 1488 François II added outworks, a great moat and five artillery towers.

The walls give their name to the Fête des remparts, a medieval festival created in 1982 and held every two years, when the streets fill with costumed parades and markets. The name Dinan is also borne by the residence of the sub-prefect on the promontory of the vanished Châteauganne motte, the town's first defensive work, destroyed around 1170.

The walls form an irregular quadrilateral following the escarpments on the east, south and west sides; the flattest, most exposed ground is to the north. The Porte Saint-Malo retains its lower section, possibly from the 13th century, and the Porte Saint-Louis was pierced in 1620 between the Penthièvre and Coëtquen towers to open the road to Rennes.

The 1154 account by the Arab geographer Al-Idrisi describes Dinan as a stone-walled trading town and a port shipping goods in all directions, though historian Stéphane Gesret considers this an exaggeration. The residence of the sub-prefect still stands on the promontory where the 11th-century castle mound, the "vieil chastel" or Châteauganne, was destroyed around 1170.