Ukraine gained independence after the collapse of the Soviet Union in 1991 and has since veered between seeking closer integration with Western Europe and reconciliation with Russia, which supplies most of the country's energy.
Europe's second largest country, Ukraine is a land of wide, fertile agricultural plains, with large pockets of heavy industry in the east.
While Ukraine and Russia share common historical origins, the west of the country has closer ties with its European neighbours, particularly Poland, and Ukrainian nationalist sentiment is strongest there.
A significant minority of the population of Ukraine use Russian as their first language, particularly in the industrialised east. In Crimea, an autonomous republic on the Black Sea which was part of Russia until 1954, ethnic Russians make up about 60% of the population. The Russian Black Sea Fleet is based there.
At a glance
- Politics: Mass protests force out pro-Russian President Viktor Yanukovych in 2014. An interim government is preparing new elections
- Economy: Dependence on steel exports makes Ukraine vulnerable to global financial turmoil. Mr Yanukovych's policies and months of political chaos leave the country short of funds
- International: Russian armed intervention in Crimea puts Ukraine at the centre of a stand-off between Moscow and the West
Country profiles compiled by BBC Monitoring
Crimea is also the homeland of the Crimean Tatars, whom Stalin accused of collaborating with the Nazis and deported to Central Asia in 1944. More than 250,000 have returned since the late 1980s. The rest of the population of the peninsula consists of Ukrainians.
In 1932-1933, Stalin's programme of enforced agricultural collectivisation brought famine and death to millions in Ukraine, the bread basket of the USSR. Not until its twilight years did the Soviet Union acknowledge the extent of the suffering.
News of another Soviet-era calamity, the 1986 accident at the Chernobyl nuclear power station, rang alarm bells around the world immediately. About 8% of Ukraine's territory was contaminated as were large areas in neighbouring Belarus. Millions have suffered as a result.Independence
The first president after independence, former Communist Party official Leonid Kravchuk, presided over rapid economic decline and runaway inflation. His successor, Leonid Kuchma, oversaw a steady economic recovery, but was accused by the opposition of conceding too much to Russian economic interests.
This opposition to Mr Kuchma grew, further fed by discontent at controls on media freedom, manipulation of the political system and cronyism.
The authorities' attempt to rig the 2004 presidential elections led to the "Orange Revolution", with reference to the colour of the main opposition movement.Europe or Russia?
Mass protests, a revolt by state media against government controls and the fracturing of the governing coalition brought in European-Union mediation and a re-run of the election.
A fragile alliance of anti-Kuchma forces united behind pro-Western former prime minister Viktor Yushchenko, who won the presidency.
Mr Yushchenko succeeded in carrying out some democratic reform, but moves towards Nato and EU membership were slowed by divided public opinion in Ukraine and Western reluctance to antagonise a resurgent Russia.
Rivalry with his prime minister, Yulia Tymoshenko, soured into open antagonism, and neither proved able to cope with the worldwide economic downturn after 2008.
Their opponent in the Orange Revolution, Viktor Yanukovych, won the 2010 presidential election. He swiftly re-oriented foreign and trade policy towards Russia, clamped down on media freedom, and had various opponents, most prominently Ms Tymoshenko, imprisoned in trials seen at by many as politically-motivated.
Although trade with EU countries now exceeds that with Russia, Moscow is the largest individual trading partner. Ukraine depends on Russia for its gas supplies and forms an important part of the pipeline transit route for Russian gas exports to Europe.
Moves to reach an association agreement with the EU - seen as a key step towards eventual EU membership - again fuelled tensions with Russia, and the government's decision to drop the agreement brought tens of thousands of protesters out onto the streets in November 2013, eventually forcing the collapse and flight of the Yanukovych government in violent chaos four months later.
As an opposition-led interim government Ukraine prepares for fresh elections, Moscow brings international tension to crisis point by sending troops to Crimea to back pro-Russian activists campaigning for secession from Ukraine.