Ukraine (Ukrainian: Україна, romanized: Ukraïna, pronounced [ʊkrɐˈjinɐ] (listen)) is a country in Eastern Europe. It is the second-largest European country after Russia, which it borders to the east and northeast. It is also bordered by Belarus to the north; by Poland, Slovakia, and Hungary to the west; and by Romania and Moldova to the southwest; with a coastline along the Black Sea and the Sea of Azov to the south and southeast. Kyiv is the nation's capital and largest city. Ukraine's state language is Ukrainian; Russian is also widely spoken, especially in the east and south.

During the Middle Ages, Ukraine was the site of early Slavic expansion and the area later became a key centre of East Slavic culture under the state of Kievan Rus', which emerged in the 9th century. The state eventually disintegrated into rival regional powers and was ultimately destroyed by the Mongol invasions of the 13th century. The area was then contested, divided, and ruled by a variety of external powers for the next 600 years, including the Polish–Lithuanian Commonwealth, the Austrian Empire, the Ottoman Empire, and the Tsardom of Russia. The Cossack Hetmanate emerged in central Ukraine in the 17th century, but was partitioned between Russia and Poland, and ultimately absorbed by the Russian Empire. Ukrainian nationalism developed, and following the Russian Revolution in 1917, the short-lived Ukrainian People's Republic was formed. The Bolsheviks consolidated control over much of the former empire and established the Ukrainian Soviet Socialist Republic, which became a constituent republic of the Soviet Union when it was formed in 1922. In the early 1930s, millions of Ukrainians died in the Holodomor, a man-made famine. The German occupation during World War II in Ukraine was devastating, and seven million Ukrainian civilians were killed, including the majority of Ukrainian Jews.

Ukraine gained independence in 1991 as the Soviet Union dissolved, and declared itself neutral. A new constitution was adopted in 1996. A series of mass demonstrations, known as the Euromaidan, led to the establishment of a new government in 2014 after a revolution. Russia then unilaterally annexed Ukraine's Crimean Peninsula; and pro-Russian unrest culminated in a war in the Donbas between Russian-backed separatists and government forces in eastern Ukraine. Russia launched a full-scale invasion of Ukraine in February 2022. Since the outbreak of war with Russia, Ukraine has continued to seek closer ties with the United States, European Union, and NATO.

Ukraine is a unitary state with a semi-presidential system. Although a developing country it is the poorest country in Europe by nominal GDP per capita, and corruption remains a significant issue. However, due to its extensive fertile land, pre-war Ukraine was one of the largest grain exporters in the world. It is a founding member of the United Nations, as well as a member of the Council of Europe, the World Trade Organization, and the OSCE. It is in the process of joining the European Union and has submitted an application for NATO membership.