From longer the Wikipedia page [1]
The Autonomous Republic of Crimea (Ukrainian: Автономна Республіка Крим, Avtonomna Respublika Krym; Russian: Автономная Республика Крым, Avtonomnaya Respublika Krym; Crimean Tatar: Qırım Muhtar Cumhuriyeti, Къырым Мухтар Джумхуриети, Ҡырым Мухтар Җумхуриети), an autonomous republic of Ukraine encompassing most of Crimea, was annexed by the Russian Federation in 2014. Crimea had previously come under Russian control in 1783 but was transferred, within the USSR, from the Russian SFSR to the Ukrainian SSR in 1954. Later, following a referendum on 20 January 1991, it was upgraded to the status of an autonomous republic within the Ukrainian SSR. When the Soviet Union collapsed in 1991 and Ukraine became an independent country, Crimea remained part of the newly independent Ukraine. Despite this, by 2013 the majority of Russians still believed that Crimea was part of Russia