Yuzhno-Sakhalinsk is a city on Sakhalin Island, Russia, administrative center of the SakhalinRegion, which includes whole island and the Kurils. In Japanese, it was known as Toyohara.

The city is on the Susuya River (also called the Black River). The population of the city is about 175,085 (2002 Census). It is served by Yuzhno-Sakhalinsk Airport.

 The city went from the small Russian settlement founded by convicts in 1882 as Vladimirovka, to Toyohara (meaning "Valley of the fecundity"), the prefect capital of Japanese Karafuto after the signing of the 1905 Portsmouth Peace Treaty, and then, after the end of World War II it went back to Russia as Yuzhno-Sakhalinsk.

The Treaty of Portsmouth, signed in Portsmouth, New Hampshire, on September 5, 1905, brought an end to the Russo-Japanese War of 1904–1905. Japan was awarded the southern half of Sakhalin Island, and was leased the Liaodong Peninsula, and its Russian rail system in southern Manchuria.

Today things are looking up for Yuzhno-Sakhalinsk, ExxonMobil and Shell have been investing heavily in the area, although most of this has been on the northern half of Sakhalin. The demand for natural resources by the Japanese, Chinese, and South Koreans are giving the entire island an opportunity for continued prosperity. There has been significant criticism, including from PolPred Kamil Iskhakov, that Sakhalin is not caring for its citizens. Despite being awash in gas deposits and gas companies, the regional administration does not yet have plans for installation of gas service on the island. The oblast also continues to have the highest rate of juvenile crime in all of Russia, and more than 40% of its businesses are unprofitable.

Most residents of the city are Russians, but there is also a sizable population of Koreans as well. Of 43,000 Sakhalin Koreans, half are estimated to live in Yuzhno-Sakhalinsk, making them roughly 12% of the town's population. Smaller numbers of indigenous minorities, such as Ainu, Nivkhs, and Oroks can also be found.