Mikhail Gorbachev was the last leader of the Soviet Union, serving from 1985 until its dissolution in 1991. He is best known for his policies of glasnost (openness) and perestroika (restructuring), which aimed to reform the political and economic systems of the USSR. These changes encouraged more transparency and reduced government control, leading to greater public discussion and criticism. Gorbachev's leadership played a significant role in ending the Cold War and reducing tensions between the Soviet Union and the United States. His efforts to promote disarmament and improve international relations earned him the Nobel Peace Prize in 1990. However, his reforms also contributed to the eventual collapse of the Soviet Union.