[2] The two countries do not share a terrestrial border, although they did during the period 1905–1945 when the island of Sakhalin was split between Japan and the Russian Empire (and later the USSR).

The Treaty of Shimoda (1855) divided the Kuril Islands, creating a maritime boundary between the Japanese Etorofu (Iturup) in the south and the Russian Urup in the north.

By the Treaty of Portsmouth, which concluded the war, Russia ceded the southern half of Sakhalin to Japan (incorporated as Karafuto Prefecture), while Japanese troops withdrew from its northern half; thus the two countries the first time in their history shared a land border, which ran along the 50th parallel north across the entire island of Sakhalin, from the Strait of Tartary to the Sea of Okhotsk.

[8][9] Even though the USSR and Japan reestablished diplomatic relations a decade later (the Soviet–Japanese Joint Declaration of 1956), no peace treaty or maritime boundary agreement between the two countries has been signed.

Iturup, Shikotan, Kunashir and Habomai), which were occupied by the Soviet Union in 1945 and incorporated into its Sakhalin Oblast.