Blaye (French: [blaj] ⓘ; Occitan: Blaia pronounced [ˈblajɔ]) is a commune and subprefecture in the Gironde department in Nouvelle-Aquitaine in southwestern France.

[3] Fortified since antiquity, this eminently strategic site located on the bank of a large river, was modernized at the end of the 17th century, thanks to Vauban.

In 1685, the Commissaire general des fortifications of Louis XIV proposed the construction of a real lock on the Gironde in order to "take control of the river" and to hold Bordeaux in case of a revolt.

Dominating the urban landscape, this imposing building has been listed as a UNESCO World Heritage Site since 2008,[4] as part of a group of structures engineered by Vauban, in testimony to their global influence on military architecture and planning over the next few centuries.

The town has a citadel built by Vauban on a rock beside the river, which contains the ruins of a medieval castle, Château des Rudel(fr), and the ruins of Basilica of Saint-Romain, which holds the tomb of Charibert II, king of Aquitaine, and son of Clotaire II.