A chronology of key events:
500 BC - Thracian tribes settle in what is now southeastern Bulgaria. They are subsequently subjugated by the Macedonian king Alexander the Great and later by the Roman Empire.
681 - Bulgarian state established.
890s - The earliest form of the Cyrillic alphabet - later versions of which are now used in dozens of Slavonic languages - is created by Bulgarian scholars.
1018-1185 - Bulgaria is part of Byzantine empire.
1396 - Ottoman Empire completes conquest of Bulgaria. Next five centuries are known as era of the "Turkish yoke".
Sofia has been ruled by Romans and Ottomans
1879: City becomes capital of new Bulgarian nation
Population: 1.2 million
1876 - Nationwide uprising against Ottoman rule is violently suppressed.
1878 March - Treaty of San Stefano - signed by Russia and Turkey at the end of their war of 1877-78 - recognises an autonomous Bulgaria.
1878 July - Treaty of Berlin creates much smaller Bulgarian principality. Eastern Rumelia remains under Ottoman rule.
1886 - Eastern Rumelia is merged with Bulgaria.
1887 - Ferdinand of Saxe-Coburg-Gotha elected prince.
1908 - Bulgaria declares itself an independent kingdom. Ferdinand assumes title of tsar.
1914-18 - World War I. Bulgaria allies itself with Germany. Some 100,000 Bulgarian troops are killed, the most severe per capita losses of any country involved in the war.
1939-45 World War II - Soviet army invades German-occupied Bulgaria in 1944. Soviet-backed Fatherland Front takes power.
1946 - Monarchy abolished in referendum and republic declared. Communist Party wins election. Georgi Dimitrov elected prime minister.
1947 - New constitution along Soviet lines establishes one-party state. Economy and industry sectors nationalised.
1954 - Todor Zhivkov becomes Communist Party general secretary. Bulgaria becomes staunch USSR ally.
1971 - Zhivkov becomes president.
1978 - Georgi Markov, a BBC World Service journalist and Bulgarian dissident, dies in London after apparently being injected with poison from the tip of an umbrella.
1984 - Zhivkov government tries to force Turkish minority to assimilate and take Slavic names. Many resist and in 1989 some 300,000 flee the country.
End of Communist era
1989 - Reforms in the Soviet Union inspire demands for democratisation.
Zhivkov ousted. Multiparty system introduced. Opposition Union of Democratic Forces (UDF) formed.
1990 - Economic crisis. Communist Party reinvents itself as Bulgarian Socialist Party (BSP) and wins free parliamentary elections.
Dissident Georgi Markov; given Bulgaria's highest honour in 2000
President Petar Mladenov resigns and parliament appoints UDF's Zhelyu Zhelev.
BSP government collapses amid mass demonstrations and general strike.
1991 New constitution proclaims Bulgaria a parliamentary republic and provides broad range of freedoms.
UDF wins election.
1992 - Zhelev becomes Bulgaria's first directly-elected president. UDF government resigns. Lyuben Berov heads non-party government.
Todor Zhivkov sentenced to seven years in prison for corruption in office.
1993 - Mass privatisation programme.
1994 - BSP returns to power in general election.
1995 - BSP's Zhan Videnov becomes prime minister.
1996 - Financial turmoil. Petur Stoyanov replaces Zhelev as president.
Bulgarian Supreme Court overturns Zhivkov's conviction.
Videnov resigns as prime minister and chairman of the BSP.
1997 - Mass protests over economic crisis. Opposition boycotts parliament and calls for elections.
Interim government installed until elections, when UDF leader Ivan Kostov becomes prime minister.
Bulgarian currency pegged to German mark.
1999 - Protracted demolition attempts on marble mausoleum of first communist leader Georgi Dimitrov become national joke.
2000 - Post-communist prosecutors close file on Georgi Markov case. In December Markov is awarded Bulgaria's highest honour, the Order of Stara Planina, for his contribution to Bulgarian literature and his opposition to the communist authorities.
2001 June - Former King Simeon II's party, National Movement Simeon II, wins parliamentary elections. Simeon becomes premier in July.
Communist-era relics find a new use in the capital
2001 November - Thousands march through Sofia on 100th day of Simeon's premiership, saying he has failed to improve living standards.
Socialist Party leader Georgi Parvanov wins presidency in an election with the lowest turnout since the fall of communism. He vows to improve people's lives and to speed up EU and Nato entry.
2001 December - Parliament agrees to destroy Soviet-made missiles by late 2002, ahead of Nato membership.
2004 March - Bulgaria is admitted to Nato.
2005 August - Socialist Party led by Sergei Stanishev tops the poll in general elections. After weeks of wrangling the main parties sign a coalition deal under which he becomes prime minister.
2005 December - Bulgaria's contingent of 400 light infantry troops leaves Iraq. In February 2006 parliament agrees to dispatch a non-combat guard unit.
2006 December - Bulgarian officials condemn death sentences handed to five Bulgarian nurses and a Palestinian doctor by a Libyan court. The six were found guilty of deliberately infecting Libyan children with the HIV virus.
Bulgaria joins EU
2007 January - Bulgaria and Romania join the European Union, raising the EU membership to 27.
2007 June - The European Commission calls on Bulgaria to do more to combat corruption.
2007 July - The death sentences against six foreign medical workers in the HIV case in Libya are commuted to life in prison. They are repatriated to Bulgaria under a deal with the European Union.
2008 February - European Commission interim report says Bulgaria and Romania have failed to show convincing results in their anti-graft drives.
2008 March - European Union freezes some infrastructure subsidies over corruption in the traffic agency.
2008 April - European Union calls on Bulgaria to take urgent action after two prominent gangland killings, including a senior figure in the nuclear industry.
Interior Minister Rumen Petkov resigns over police officers accused of passing state secrets to alleged crime bosses.
Government reshuffled in order to combat organised crime and wave of contract killings. Ambassador to Germany, Meglena Plugchieva, appointed deputy prime minister without portfolio to oversee use of EU funds.
2008 July - European Commission suspends EU aid worth hundreds of millions of euros after series of reports criticise Bulgarian government for failing to take effective action against corruption and organised crime.
2008 September - European Commission permanently strips Bulgaria of half of the aid frozen in July over what it says is the government's failure to tackle corruption and organised crime.
2009 January - Russia's gas dispute with Ukraine cuts supplies to Bulgaria, resulting in a severe energy shortage lasting several weeks and widespread anger at the government's energy policies.
2009 June - Workers rally to protest at government's handling of economic crisis.
2009 July - General election is won by the centre-right GERB party led by Sofia mayor Boiko Borisov.
2010 January - Boris Tsankov, a prominent crime journalist who specialised in reporting on the mafia in Bulgaria, is shot dead in Sofia.
2010 June - EU expresses concern over reliability of Bulgarian national statistics and says these may have to be subjected to EU scrutiny.
2010 July - Former PM Sergei Stanishev is accused of failing to return files containing state secrets relating to security and organised crime after losing the 2009 election, and is charged with mishandling classified documents.
2010 September - EU calls on Bulgaria to take urgent action to tackle crime and corruption.
2010 November - Bulgaria and Russia agree to speed up construction of South Stream pipeline that will carry gas from Russia to Europe via Black Sea.
2010 December - Government-appointed commission finds that 45 senior Bulgarian diplomats were secret service agents during the communist era.
France and Germany block Bulgaria from joining Schengen passport-free zone, saying it still needs to make "irreversible progress" in fight against corruption and organised crime.
2011 September - Anti-Roma demonstrations in Sofia and elsewhere following the death of a youth who was hit by a van driven by relatives of a Roma kingpin.
2011 October - Outgoing construction minister Rosen Plevneliev, the candidate of the centre-right GERB party of Prime Minister Borisov, beats the Socialist candidate in the presidential election.
2012 January - Bulgaria becomes the second European country after France to ban exploratory drilling for shale gas using the extraction method called "fracking" after an overwhelming parliamentary vote.