L'Isle-sur-le-Doubs () is a commune in the Doubs department in the Bourgogne-Franche-Comté region in eastern France.
The communes is situated northeast of Besançon and southwest of Montbéliard. The town lies at the foot of a cliff, so expansion took place on the other side of the river Doubs.
The town of l'Isle-sur-le-Doubs was formed from the merging of the villages of Fusnans, Carnans, and Uxelles. It belonged originally to the abbey of Les Trois Rois, and was then ceded to the Count of Neufchâtel, who built his castle there in 1230, only the foundations of which remain.
The inhabitants of the commune are called l'Islois in French.
The commune has a three-star camping ground and attracts many tourists who go fishing in the Doubs. Hiking trails are also numerous in the surrounding countryside.