Coordinates: 43°29′37″N 1°28′30″W / 43.4936°N 1.475°W / 43.4936; -1.475

Bayonne (French pronunciation: [bajɔn]; Gascon and Basque: Baiona) is a city and commune in south-western France at the confluence of the Nive and Adour rivers, in the Pyrénées-Atlantiques department, of which it is a sub-prefecture. It belongs to both vernacular cultural regions of Basque Country and Gascony.

Together with nearby Anglet, Biarritz, Saint-Jean-de-Luz, and several smaller communes, Bayonne forms an urban area with 178,965 inhabitants at the 1999 census, 40,078 of whom lived in the city of Bayonne proper (44,300 as of 2004 estimates).

The communes of Bayonne, Biarritz, and Anglet have joined into an intercommunal entity called the Agglomération Côte Basque-Adour (formerly Communauté d'agglomération de Bayonne-Anglet-Biarritz (BAB) prior to 2010).

In the 3rd century AD, the area was the site of a Roman castrum, named Lapurdum. It was a military site, but not a port. In 840, the Vikings appeared before Lapurdum. In 842, with their chieftain Björn Ironside they launched a large-scale inland offensive and settled outside the city on the river bank^{[citation needed]}. Lapurdum was an oppidum and they needed a port. Bayonne (from Basque ibai, "river") became a key place on the route between the Adour and Ebro Rivers, which served as a kind of link between the Atlantic Ocean and the Mediterranean Sea.^{[citation needed]} This commercial route was the main goal of Danish invaders in France. By this route, they could easily reach Muslim-controlled Tortosa, which was the main marketplace in Europe dealing with slaves.^{[citation needed]}