The article presents a comprehensive study of the formation of the multinational composition of the population of the Sakhalin Region, covering the period from the mid-19th century to the present. Particular attention is paid to the analysis of the historical prerequisites that determined the formation of the ethnocultural landscape of the region. Significant changes in the ethnocultural composition of the population occurred after the end of World War II and the inclusion of all of Sakhalin into the USSR. The deportation of the Japanese population and the influx of Soviet citizens from various regions of the country radically changed the demographic picture. Repre-sentatives of various nationalities arrived in Sakhalin, mainly Russians, Ukrainians, Belarusians, as well as Ta-tars, Koreans and others. The study is structured according to the key stages and factors in the formation of the main groups of the population of the island region. The results obtained make it possible to trace the dynamics of the ethnocultural development of the region, identify the main trends and factors influencing the formation of the multinational population of the Sakhalin region.