The study focuses on a complex burning issue that arose in Ukrainian-Russian interstate relations after the downfall of the USSR. The establishment of control over the Crimean peninsula became a priority task of the Russian Federation, which repeatedly made attempts to capture it during 1990-2000. However, the well coordinated actions of the Ukrainian authorities and law enforcement structures allowed repelling the most dangerous attacks in 1993-1994, 2003. New aggravation on the peninsula and in Russian-Ukrainian relations generally occurred in 2005-2009. The deployment of the naval forces of the Russian Black Sea Fleet in Ukraine exacerbated the disintegration tendencies in Crimea and Russia’s geopolitical role in the Black Sea region. The preservation of the Russian military contingent on the peninsula contributed to the annexation of Crimea, the preparation for which began in 2013. The annexation of the territory of the Autonomous Republic of Crimea by Russia has negative political, economic, social, cultural, ecological consequences for the peninsula and Ukraine.