Iturup (Ainu イト゚ルㇷ゚; Japanese 択捉島, Etorofu; Russian Итуруп) is the biggest island of the Kuriles, located in the Sakhalin Oblast of Russia. Although Iturup is administered as part of Russia, Japan maintains a claim to it along with the other three islands (see Kuril Island conflict).

• Area - 6725 sq km
• Length - 200 km
• Width - 7-27 km

Iturup consists of volcanic massifs and mountain ridges. The highest peak is 1634 m. The shores of the island are high and abrupt. The vegetation mostly consists of spruce, larch, pine, fir, and mixed deciduous forests with alder, lianas and Kuril bamboo underbrush. The mountains are covered with birch and Siberian Dwarf Pine scrub, herbaceous flowers or bare rocks.

The principal city is Kurilsk .