- 6000–5000 BC
Bulgaria’s earliest Neolithic settlers occupy caves, abandoning them around 5000 BC for mud huts. Farming develops.
- 4000–1000 BC
Thracian tribes dominate modern-day Bulgaria; around 3000 BC, settlements include coastal Mesembria; around 2000 BC they expand into Greece and Anatolia.
- 611 BC
Greek settlers from the Anatolian city-state of Miletus establish Apollonia Pontica (Sozopol) on the Black Sea coast – the first classical democracy on Bulgarian territory. All males over 18 can vote.
- 335 BC
Macedonian king Alexander the Great extends the Thracian holdings of his father Philip II by marching to the Danube, the northernmost border of his massive empire.
- AD 46
Rome annexes the eastern Balkans and modern-day Bulgaria is divided into provinces: Thrace (in the south), Moesia (in the north) and Ulpia Serdica (today's Sofia) as the capital of Inner Dacia.
Roman emperor Diocletian establishes the ‘Tetrarchy’ (rule of four), reorganising imperial administration. Regional ‘capitals’ are established, including Serdica (Sofia), which becomes important.
Forces of Attila the Hun cross the Danube, sweeping into Roman territory and sacking Serdica and Philipopolis (Plovdiv), forcing Rome to pay tribute in gold.
After Turkic Bulgar tribes sweep down from the Black Sea steppes, Khan Asparuh establishes the First Bulgarian Empire at Pliska. Centuries of chronic fighting with Byzantium ensue.
Khan Krum dies unexpectedly while preparing to besiege Constantinople; the Bulgars make peace two years later.
Byzantine monks Kiril and Metodii undertake a mission to the Moravian Slavs; their monk-disciples later spread the Cyrillic alphabet in Ohrid, in Bulgarian-controlled Macedonia.
Byzantine Orthodox prelates baptise Knyaz Boris and his court; Constantinople's dramatic competition with the Pope only ends in 870, when Bulgaria wins national-church status.
Boris’ third son, Tsar Simeon (r 893–927) expands borders from Romania and Bosnia to the Peloponnese, becoming Europe's strongest power.
Byzantines capture and burn the Bulgarian capital, Preslav; the leadership relocates to Ohrid, their capital until the Byzantine reconquest in 1018.
Byzantine forces win decisively at the Battle of Kleidion/Belasitsa in southwestern Bulgaria, auguring the Bulgarian Empire's demise four years later.
Aristocrat brothers Asen and Petâr rebel against a weakening Byzantium, establishing the Second Bulgarian Empire, with Veliko Târnovo the capital. Tsar Ivan Asen II (1218–41) expands Bulgaria’s borders.
Bulgaria’s last native king, Tsar Ivan Shishman (1371–96), is defeated and Bulgaria is annexed by the Ottoman Empire, beginning 500 years of harsh Islamic rule.
A Hungarian-led Crusade against the Turks ends disastrously at the Battle of Varna.
The First Târnovo Uprising against Turkish rule briefly liberates Veliko Târnovo. A new tsar is crowned, but the revolt is brutally crushed. Thousands of Bulgarians flee to Wallachia.
Austrian victories against the Turks inspire revolts in northern Bulgaria, but the so-called Second Târnovo Uprising is squashed.
The National Revival era; monk Paisii Hilendarski’s groundbreaking Slav-Bulgarian History captivates Bulgarians. By the 19th century, Bulgarian-language education (1840s) is allowed and the Bulgarian Orthodox Church (1870) is established.
The Crimean War brings British and French troops to Bulgaria, with Varna an important garrison; Turkey is compelled to open up Bulgaria to international trade.
Koprivshtitsa's April Uprising is suppressed; civilian massacres cause international outrage. The Ottomans reject Bulgarian autonomy at the November Constantinople Conference.
Russo-Turkish War; Tsar Alexander II's army invades Bulgaria and destroys the Ottoman forces. The resulting Treaty of San Stefano envisages the Turks ceding 60% of the Balkan Peninsula to Bulgaria.
Only four months after San Stefano, Western European powers fearing Russian expansionism enforce the Berlin Treaty, drastically limiting Bulgarian land gains.
A bloodless coup sees Bulgaria reunited with the Ottoman-controlled southlands. Turkish armies mobilise, while a Serbian invasion is defeated. Bulgaria's new borders are internationally recognised.
Amid internal Turkish political chaos, Prince Ferdinand declares full independence from Turkey and becomes tsar of the new Bulgarian kingdom.
Bulgaria and neighbouring states fight the Ottomans in the First Balkan War (1912), reclaiming territory. Dissatisfied with its share, Bulgaria attacks allies Greece and Serbia in the Second Balkan War (1913), losing hard-won territory.
Bulgaria joins the Germans in WWI; defeated, the Treaty of Neuilly-sur-Seine punishes Bulgaria by awarding land to its neighbours, while the government faces crippling reparation payments.
Prime Minister Aleksandar Stamboliyski is assassinated by right-wing military supporters of Macedonian revolutionaries. A communist uprising is brutally repressed and the communist party banned.
Southern Dobrudzha, occupied by Romania since 1913, is returned to Bulgaria for a nominal fee; a population exchange follows.
After first declaring neutrality, Bulgaria joins the Axis powers after German troops are stationed along the Danube, and declares war on Britain and France, but not on the Soviet Union.
After winning 1945 elections, the communists under Georgi Dimitrov declare the People’s Republic of Bulgaria, with Soviet backing.
After a show trial, the Bulgarian Supreme Court sentences deputy prime minister Traicho Kostov to death on grounds of encouraging anti-Soviet feeling. Similar staged trials of prominent communists, often with confessions obtained through torture, followed.
The government initiates a mass agricultural collectivisation program – the Great Leap Forward – promising a five-year modernisation plan in just three years.
In one of the most infamous Cold War espionage events, Bulgarian dissident writer Georgi Markov is assassinated in London with a poisoned umbrella tip by a Bulgarian secret agent.
A nationalistic campaign to assimilate the ethnic Turkish population causes a mass exodus of Turks, though many return after communism ends.
Democratic revolutions see Todor Zhivkov’s communist regime collapse; Zhelyu Zhelev becomes Bulgaria's first non-communist head of state.
Transition times; massive inflation, corruption and plummeting wages make Bulgaria Europe's poorest country. Successive governments fail, while organised crime flourishes.
Bulgaria’s formerly exiled child-king, Simeon Saxe-Coburg, becomes prime minister.
Bulgaria, along with other former Warsaw Pact nations, joins NATO.
On 1 January, despite European misgivings over stalled reforms, Bulgaria joins the EU, becoming its first 'Cyrillic' country. Brussels pressures the government to tackle organised crime, judiciary shortcomings and environmental problems.
Year-long protests against the Plamen Oresharski government, and loss of faith in its ability to tackle Bulgaria's banking crisis, causes it to topple on 23 July. Boyko Borisov's coalition government steps in on 7 November.