The Gironde estuary (/ʒɪˈrɒnd/ zhi-ROND, US usually /dʒɪˈ-/ ji-; French: estuaire de la Gironde, French pronunciation: [ɛstɥɛʁ də la ʒiʁɔ̃d]; Occitan: estuari de [la] Gironda, Occitan pronunciation: [estyˈaɾi ˈde lo dʒiˈɾundo]) is a navigable estuary (though often referred to as a river) in southwest France and is formed from the meeting of the rivers Dordogne and Garonne just downstream of the centre of Bordeaux. Covering around 635 km (245 sq mi), it is the largest estuary in western Europe.
Giving its name to the French département Gironde, the Gironde estuary is approximately 75 km (47 mi) long and 3–12 km (1.9–7.5 mi) wide. It is subject to very strong tidal currents and great care is needed when navigating the estuary by any size or type of boat.