While Ukraine and Russia share common historical origins, the west of the country has close ties with its European neighbours, particularly Poland, and Ukrainian nationalist sentiment is strongest there.
A significant minority of the population of Ukraine are Russians or use Russian as their first language. Russian influence is particularly strong in the industrialised east, as well as in Crimea, an autonomous republic on the Black Sea which was part of Russia until 1954. The Russian Black Sea Fleet is based there.
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.
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.
The first president after independence, former Communist Party official Leonid Kravchuk, presided over a period of economic decline and runaway inflation. His successor, Leonid Kuchma, oversaw steady economic recovery, but was accused of conceding too much to Russian economic interests.
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.
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, from pro-Western democrats, socialists, business interests and nationalists united behind opposition leader and former prime minister Viktor Yushchenko, who won the presidency.
Mr Yushchenko secured the transparency of the democratic process, the rule of law and media freedom, but his efforts to move towards Nato and EU membership made slow progress in the face of Western reluctance to antagonise a resurgent Russia and a divided public opinion in Ukraine itself.
Rivalry with his prime minister, Yuliya Tymoshenko, soured into open antagonism, and neither proved able to cope with the worldwide economic downturn after 2008.
Their opponent in the 2004-2005 Orange Revolution, Viktor Yanukovych, won the 2010 presidential election. He swiftly re-oriented foreign and trade policy towards Russia and clamped down on media freedom. He also had various oppenents, most prominently Ms Tymoshenko, imprisoned in trials regarded at home and abroad 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.
A dispute over price rises prompted Russia briefly to cut supplies for use by Ukraine in January 2006 and raised concerns across Europe too. The gas was switched back on only after Ukraine agreed to pay almost twice the former price, which rose sharply again for 2007. In January 2009, Russia again cut gas supplies in a row over unpaid fees.
The Ukrainian economy's dependence on steel exports made it particularly vulnerable to the effects of the global financial crisis of 2008, and in October of that year the country was offered a $16.5bn (£10.4bn) loan by the International Monetary Fund (IMF).
President: Viktor Yanukovych
Mr Yanukovych was declared the winner of the second round of voting in the 2010 presidential election, with a 3.48% lead over Prime Minister Yulia Tymoshenko.
His inauguration as president marked the climax of Viktor Yanukovych's political comeback. First, he overcame the disgrace of the 2004/05 presidential defeat and retained the leadership of the Party of the Regions, leading it back into power as prime minister in 2006-2007.
He narrowly lost the 2007 parliamentary elections, but benefited from discord between President Yushchenko and Mrs Tymoshenko and went on to capitalise on discontent over the government's failure to cope with the global economic crisis after 2008.
Born into a poor family in Donetsk Region, eastern Ukraine's industrial powerhouse, in 1950, Mr Yanukovych had a troubled childhood and was twice jailed for violent crimes in his youth. On release he went to work in the local transport industry, where he rose through the ranks of management under the patronage of cosmonaut and local Soviet MP Georgi Beregovoi.
He established a political power base in the Donetsk Region administration, becoming governor in 1997 and later head of the council. There he built close ties to local tycoon Rinat Akhmetov.
President Kuchma appointed him prime minister in 2002, and nominated him as presidential candidate for the governing coalition of political and business interests in 2004.
Mr Yanukovych has worked hard to distance himself from the scandals of the pre-2004 period and from accusations of being Russia's placeman. He says that his aim is to balance relations between Russia and the European Union, with EU integration as a "strategic aim".
However, the speed with which he agreed in April to extend the Russian lease on the Black Sea Fleet base in Crimea raised opposition suspicions of this balance.
His government regularly earns criticism from the EU, in particular of the imprisonment of Mrs Tymoshenkoover abuse of power while negotiating a gas deal with Russia in 2009.
Prime minister: Mykola Azarov
Mykola Azarov, an ethnic Russian born in Russia, is a close associate of President Yanukovych and succeeded him as head of the Party of Regions in 2010. After the government of Mr Yanukovych's chief rival, Yuliya Tymoshenko, fell in a vote of confidence in March 2010, Mr Azarov formed a coalition with the Communists and the centrist Lytvyn Bloc.
Mr Azarov was head of the tax administration in 1996-2002, and his term as finance minister during Mr Yanukovych's subsequent premiership oversaw dramatic economic growth.
He was briefly acting prime minister during the presidential election crisis of 2004-2005, and resumed the post of finance minister during the Yanukovych government of 2006-2007.
A mining specialist, Mr Azarov is a technocrat with neither a political base nor ambitions of his own. His poor command of Ukrainian is often highlighted by his opponents, who see him as a symbol of Mr Yanukovych's alleged pro-Russian orientation.
Television dominates the media scene in terms of audiences and advertising revenue.
Many outlets are privately-owned. Commercial TVs, particularly Inter TV and 1+1, attract the biggest share of the audience. The FM band in Kiev is home to more than 20 radio stations.
Many newspaper titles have Ukrainian and Russian-language editions. Several of the biggest-selling tabloids publish only in Russian.
Despite an expanding advertising market, many media outlets rely on the support of wealthy sponsors.
In 2010, watchdog Reporters Without Borders (RSF) said "multiple press freedom violations" had been recorded since Viktor Yanukovych's election as head of state. RSF added that "serious conflicts of interest are menacing Ukraine's media pluralism".
There were 15.3 million internet users by June 2010 (Internetworldstats). The medium is becoming a popular source of news, with more than a dozen leading sites - neutral, pro-opposition and pro-government.