Monségur (French pronunciation: [mɔ̃seɡyʁ]; Occitan: Montsegur) is a commune in the Gironde department in Nouvelle-Aquitaine in southwestern France.

[3] Monségur is a bastide town, about 75 km (47 mi) upriver from Bordeaux in the low rolling vineyard country between the rivers Garonne in the South and the Dordogne in the North.

The layout follows a classic bastide design, with a town square surrounded by arches, narrow streets, parallel back lanes and ramparts.

The town of Monségur is located in the canton of Le Réolais et Les Bastides and the arrondissement of Langon.

The most famous annual event in surely the 24 heures du Swing de Monśegur, which has been drawing enthusiasts from all over France since 1988.