The Isère (US: /iːˈzɛər/ ee-ZAIR,[3][4] French: [izɛʁ] ⓘ; Arpitan: Isera; Occitan: Isèra) is a river in the Auvergne-Rhône-Alpes region of southeastern France.

This word is related to the Indo-European *isərós, meaning "impetuous, quick, vigorous," which is similar to the Sanskrit isiráḥ इसिरः อิสิระ with the same definition.

[6] It was probably based on the reconstructed Indo-European root *eis(ə) (and not *is), which incidentally has not been found in the Celtic languages of the British Isles.

In non-Celtic countries, we find the Isarco, a river in Northern Italy, the Éisra and Istrà in Lithuania,[6] Jizera in the Czech Republic and Usora in Bosnia and Herzegovina.

The Isère's course measures 286 kilometers (178 miles)[1] and runs through a wide variety of landscapes: from its source near the Italian border in the western Alps, it crosses the Pays de Savoie and the Tarentaise Valley, cuts between the Chartreuse and Belledonne mountain ranges, follows the Vercors Massif, passes through the Dauphiné province, and finally meets with the Rhône at the foot of the Vivarais.

The lower valley constitutes a section of the Plain of Valence [fr] (also called the Valentinois)[7] and is characterized by the river's deep, winding channel.

[2] The Isère's large seasonal fluctuations are typical of rivers fed in large part by snowmelt, with springtime flooding raising the average monthly discharge between 382 (13,500) and 500 m3/s (18,000 cu ft/s) from April to July (peaking in May and June), and low water levels in autumn and winter, from August to February, with a minimum average monthly discharge of 246 m3/s (8,700 cu ft/s) in September.