Isère (pronounced: [izɛːʁ]; Arpitan: Isera, Occitan: Isèra) is a department in the Rhône-Alpes (Rôno-Arpes in Arpitan) region in the east of France named after the river Isère.

Isère is one of the original 83 departments created during the French Revolution on March 4, 1790. It was created from part of the former province of Dauphiné. Its area has been reduced twice, in 1852 and again in 1967, on both occasions losing territory to the department of Rhône.

In 1852 in response to rapid urban development round the edge of Lyon, the (hitherto Isère) communes of Bron, Vaulx-en-Velin, Vénissieux and Villeurbanne were transferred to Rhône. In 1967 the redrawing of local government frontiers led to the creation of the Urban Community of Lyon (more recently known simply as Greater Lyon / Grand Lyon). At that time intercommunal groupings of this nature were not permitted to straddle departmental frontiers, and accordingly 23 more Isère communes (along with 6 communes from Ain) found themselves transferred to Rhône. The affected Isère communes were Chaponnay, Chassieu, Communay, Corbas, Décines-Charpieu, Feyzin, Genas, Jonage, Jons, Marennes, Meyzieu, Mions, Pusignan, Saint-Bonnet-de-Mure, Saint-Laurent-de-Mure, Saint-Pierre-de-Chandieu, Saint-Priest, Saint-Symphorien-d'Ozon, Sérézin-du-Rhône, Simandres, Solaize, Ternay and Toussieu.