Grig Island, named after Norwegian composer Edvard Grieg, is the largest of Shikotan’s satellite islets, covering an area of approximately 1.26 km². It is located off the southeastern coast of Shikotan, separated by a narrow strait 300–400 meters wide. The island has a distinctive comma-like shape, with a "head" in the north. It stretches about 2 km in length, with a width ranging from 0.4 to 1.3 km.

The island's coastline is predominantly steep and rocky, with cliffs reaching heights of 50–80 meters. The eastern part features a more gradual slope, where small streams flow into the ocean. Vegetation consists mainly of grassy meadows, with no forests or shrubs, giving the island a rugged and open landscape.

Grig Island is a protected area designated for the conservation of local seabirds. A small colony of black-tailed gulls nests here, while red foxes once inhabited the island but disappeared due to hunting activities before the area's protected status was established.

Part of the Lesser Kuril Ridge, Grig Island is administratively under the jurisdiction of Russia’s Sakhalin Oblast, specifically the Yuzhno-Kurilsky District. However, its location remains subject to territorial disputes, as Japan considers it part of Nemuro Subprefecture in Hokkaido.