Interim president: Olexander Turchynov
A long-time ally of former Prime Minister Yulia Tymoshenko, Olexander Turchynov was given interim presidential powers by parliament after President Viktor Yanukovych was driven from power by protests in 2014.
Mr Yanukovych had fled the capital after months of unrest sparked by anger at his decision to scrap a planned association agreement with the EU, and instead move closer to Russia.
The new interim president promised to form a coalition unity government and restore the country's pro-EU course.
His installation came hours after the release of Ms Tymoshenko, whose 2011 jailing for abuse of power was widely seen as political revenge by Mr Yanukovych.
Ms Tymoshenko, who leads the Fatherland party, announced her intention to stand in presidential elections set for 25 May, as did Vitaliy Klitschko, head of the rival opposition Udar party.
President (ousted): 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".
His first two years in office saw extensive concessions to Russia, such as extending the Russian lease on the Black Sea Fleet base in Crimea and moves to restrict media freedom. However, he drew the line at taking Ukraine into a customs union with Russia.
His government has regularly earned criticism from the United States, European Union and international rights groups over the imprisonment of Mrs Tymoshenko and other opposition politicians and the alleged rigging of the 2012 parliamentary elections.
Progress towards reaching an association agreement with the EU - seen as a key step towards eventual EU membership - raised the hackles of Russia, which retaliated by banning the import of certain Ukrainian products.
The government's decision to abandon the association agreement in November 2013 brought tens of thousands of protesters onto the streets of Kiev, accusing the president of bowing to Russian pressure.
After months of failed attempts to agree a compromise or disperse the protesters, the demonstrations culminated in a week of deadly violence in February that saw Mr Yanukovych flee his capital overnight, although he refused to stand down.