Overview taken from Omniglot
Ukrainian is an Eastern Slavonic language closely related to Belarusian, Polish, and Serbian. It is spoken by about 51 million people mainly in Ukraine (Україна), and also in many other countries, including Argentina, Armenia, Azerbaijan, Belarus, Brazil, Canada, Estonia, Georgia, Hungary, Kazakhstan, Kyrgyzstan, Latvia, Lithuania, Moldova, Paraguay, Poland, Romania, Russia and Slovakia.
The recorded history of the Ukrainian language began in 988, when the principality of Kyiv / Kiev (Київ) was converted to Christianity. Ukrainian religious material, including translations of the Bible, was written in Old Slavonic, the language used by missionaries to spread Christianity to the Slavic peoples.
In the 13th century, Ukraine became part of the Grand Duchy of Lithuanian and Ruthenian, an ancestor of Belarusian and Ukrainian became the main language. The remaining parts of Ukraine were taken over by Poland during the 16th century and Latin and Polish were used for official purposes. Ruthenian began to split into Ukrainian and Belarusian during this period.
The Cossacks later moved into eastern Ukraine and during the 17th century, their leader, Bohdan Khmelnytsky, invited Russia to help against Polish domination in 1648. During the reign of Catherine the Great, the Cossacks moved to the eastern frontiers of Russia, but Ukraine remained under Russian domination, and the Russians considered the Ukrainian language as little more than a dialect of Russian.
A decree in 1876 banned the printing or importing of Ukrainian books. Inspite of this, there was a revival of Ukrainian poetry and historiography during the 19th century.
Ukraine enjoyed a brief period of independence from 1918 to 1919, then was taken over by the USSR and declared a Soviet Republic. During the Soviet era, Russian was the main language of education and employment and Ukrainian was sidelined.
Ukraine declared independence in 1991. Since then many Ukrainian émigrés have returned to Ukraine, particularly from central Asia and Siberia.
Please note, the capital of Ukraine is written Київ (Kyiv) in Ukrainian, and Киев (Kiev) in Russian. It is usually written Kiev in English, however since 1995 the Ukrainian government has written it Kyiv in legislative and official acts, and this spelling is used by international organisations such as the UN, and international news sources, such as the BBC.