structural:reformatting
Soviet and modern periods

Soviet power was established on the territory of the peninsula on November 9, 1917, but the territory was occupied by the forces of Russia's pre-war allies in March 1918–March 1920. Alexandrovsky Uyezd was transformed into Murmansk Governorate by the Soviet government in June 1921. On August 1, 1927, the All-Russian Central Executive Committee (VTsIK) issued two Resolutions: "On the Establishment of Leningrad Oblast" and "On the Borders and Composition of the Okrugs of Leningrad Oblast", according to which Murmansk Governorate was transformed into Murmansk Okrug (which was divided into six districts) and included into Leningrad Oblast. This arrangement existed until May 28, 1938, when the okrug was separated from Leningrad Oblast, merged with Kandalakshsky District of the Karelian ASSR, and transformed into modern Murmansk Oblast.

All in all, the Soviet period saw a significant increase in population (from 15,000 in 1913 to 1,150,000 in 1989), although most of the population remained concentrated in the urban localities along the railroads and the sea coast. Most of the sparsely populated territories outside the urbanized areas were used for deer herding. In 1920–1940, the town of Kirovsk and several work settlements were established on the peninsula.

The Sami peoples were subject to forced collectivization, with more than half of their reindeer herds collectivized in 1928–1930. In addition, the traditional Sami herding practices were phased out in favor of the more economically profitable Komi approach, which emphasized permanent settlements over free herding. Since the Sami culture is strongly tied to the herding practices, this resulted in the Sami people gradually losing their language and traditional herding knowledge. Most Sami were forced to settle in the village of Lovozero, which became the cultural center of the Sami people in Russia. Those Sami resisting the collectivization were subject to forced labor or death. Various forms of repression against the Sami continued until Stalin 's death in 1953. In the 1990s, 40% of the Sami lived in urbanized areas, although some herd reindeer across much of the region.

The Sami were not the only people subject to repressions. Thousands of people were sent to Kola in the 1930s–1950s, and in 2007 over two thousand people—descendants of those forcibly sent there—still live on the peninsula. A significant portion of the people deported to Kola were peasants from southern Russia subjected to dekulakization. Prisoner labor was often used when building new factories and for manning those which were operational: in 1940, for example, the whole Severonikel Metallurgy Mining Complex was turned over to the NKVD system.