Poronaysk is a town located in Russia, serving as the administrative center of the Poronaysky District within the Sakhalin Oblast. It is situated on the Poronay River, approximately 288 kilometers (179 miles) north of the regional capital, Yuzhno-Sakhalinsk.
According to census data, the population of the town has fluctuated over recent decades. The 2010 census recorded a population of 16,120, following a figure of 17,954 in 2002 and 25,971 during the 1989 Soviet census.