Iturup (Russian: Итуру́п; Japanese: 択捉島), also historically known by other names, is an island in the Kuril Archipelago separating the Sea of Okhotsk from the North Pacific Ocean.

A series of a dozen calc-alkaline volcanoes running NE to SW form the backbone of the island, the highest being Stokap (1,634 m) in the central part of Iturup.

The mountains are covered with birch and Siberian Dwarf Pine scrub, herbaceous flowers (including Fragaria iturupensis, the Iturup strawberry) or bare rocks.

[4] The development of the Kuril Island arc was significantly influenced by extensive caldera-forming volcanic eruptions during the Late Neo-Pleistocene-Holocene, which introduced large amounts of pumice-pyroclastic material and tephra into the wave processing zone.

[6] The present geomorphological appearance of the isthmus is a consequence of subsequent wave and aeolian pyroclastic processing, leading to the formation of marine and lagoon terraces.

[7] A study by Afanas'ev et al.[8] focuses on examining the existence of the strait separating the southern and northern parts of Iturup Island in the mid-late Holocene from the perspective of coastal geomorphology.

Late Pleistocene explosive volcanism is considered to have been more intense and prolonged than Early Holocene events, leading to the formation of pumice deposits in the Prostor Gulf of Iturup Island.

[10] Fieldwork conducted in 2017–2018 on the Vetrovoy isthmus revealed volcanic-tectonic dislocations with a layer of beach material, suggesting the occurrence of at least two pyroclastic outbursts in the mid-Late Holocene.

The morphometric parameters of the basement terrace indicate an area elevation rate during the last phase of coastal marine accumulation that could reach 4 mm/year, slightly higher than the 3.5 m/year recorded during the last 6000 thousand years.

[12] In conclusion, several studies suggest that explosive volcanism in the middle Late Holocene significantly affected the morphotectonic plan of the Vetrovoy Isthmus area, possibly contributing to the obstruction of the strait.

Europeans are first recorded visiting this part of the Kurils in 1643[14] when the Castricum under Maarten Gerritsz Vries was exploring Hokkaido and the surrounding area for the Dutch East India Company (VOC).

[21] In 1956 the two countries agreed to restore diplomatic relations, but a peace treaty, as of 2024[update], has not been concluded due to the disputed status of Iturup and some other nearby islands.

A Soviet Anti-Air Defense (PVO) airfield, Burevestnik (English: storm-petrel), is located on the island and was until 1993 home to a number of Mikoyan-Gurevich MiG-23 fighter jets.