Belley (French pronunciation: [bəlɛ] ; Arpitan: Bèlê) is a subprefecture of the Ain department in the Auvergne-Rhône-Alpes region, France. It is the capital of the historical region of Bugey , although not its largest city, which is Oyonnax, to the north. In 2020, the commune had a population of 9,207.

Belley is of Roman origin; in the 5th century it became an episcopal see. It was the capital of the province of Bugey, which was a dependency of Savoy till 1601, when it was ceded to France. In 1385 the town was almost entirely destroyed by an act of arson, but was sequentially rebuilt by the dukes of Savoy, who surrounded it with ramparts of which little is left.