Sakhalin was originally peopled by the Nivkh, Orok, and Ainus (the latter are the main ethnic group on Hokkaido). It was explored by Cossack fur traders and Dutch merchants in the 1640s, and claimed by Russia in 1853. Under an agreement signed in 1855, the island was divided between Russia and Japan. The whole of Sakhalin become Russian in 1875, in exchange for Japanese sovereignty over the Kuril Islands; Tsarist Russia used the island's extreme remoteness to found a penal colony. Following Russia's humiliation in the Russo-Japanese War of 1904-05, the southern part of Sakhalin to 50°N was ceded to Japan. Under the Agreement reached at the Yalta Conference at the end of World War II in 1945, the Soviet government was given the right to retake the southern half. The Japanese population of over 400,000 was forcibly repatriated to Japan.

During the Soviet period, a number of military bases were built on the island; in 1983, a Korean airliner overflying Sakhalin was destroyed by a Russian fighter, with the loss of 267 lives. In May 1995, around 2,000 inhabitants of Sakhalin were killed when a major earthquake (measuring 7.5 on the Richter scale) hit the north of the island, destroying the oil-producing town of Neftegorsk, where many poorly constructed buildings of the Soviet era collapsed, crushing their inhabitants.

The northern third of Sakhalin is lowland; farther south, two Tertiary anticlinal mountain ranges (highest point 1,609 m/5,279 ft) are separated by the synclinal valley of the Poronai and Tym rivers. The island has a cool monsoonal climate. The Russian writer Anton Chekhov, in his Journey to Sakhalin (1890), described his experience in the following terms: ‘I have seen Ceylon, which is paradise, and Sakhalin, which is hell’.