Bulgaria is founded as a Khanate on the south bank of the Danube after defeating the Byzantine armies of Emperor Constantine IV south of the Danube delta.

Simeon I of Bulgaria is crowned Emperor of the first Bulgarian empire

Bulgarian tsar Ivan Asen II defeats Theodore of Epirus in the Battle of Klokotnitsa.

Bulgarian revolutionary leader Vasil Levski is executed by hanging in Sofia by the Ottoman authorities.

The April Uprising breaks out in Bulgaria.

Hristo Botev, a national revolutionary of Bulgaria, is killed in Stara Planina

Bulgaria regains its independence from Ottoman Empire according to the Treaty of San Stefano; shortly after Congress of Berlin stripped its status to an autonomous state of the Ottoman Empire.

Eastern Rumelia declares its union with Bulgaria. The Unification of Bulgaria is accomplished.

The independence of Bulgaria is proclaimed.

Bulgaria, Greece and Serbia declare war on the Ottoman Empire, joining Montenegro in the First Balkan War.

During the First Balkan War, Kardzhali is liberated by Bulgarian forces

Bulgaria, Greece, Montenegro, and Serbia (the Balkan League) sign an armistice with Turkey, ending the two-month long First Balkan War.

Balkan War: Bulgarian forces take Adrianople.

Greece and Serbia annul their alliance with Bulgaria.

Second Balkan War: delegates from Bulgaria, Romania, Serbia, Montenegro, and Greece sign the Treaty of Bucharest, ending the war.

Serbia and Bulgaria interrupt diplomatic relationship.

Bulgaria enters World War I as one of the Central Powers.

World War I: The Hindenburg Line is broken by Allied forces. Bulgaria signs an armistice.

Bulgaria's military takes over the government in a coup.

The Treaty of Lausanne, settling the boundaries of modern Turkey, is signed in Switzerland by Greece, Bulgaria and other countries that fought in World War I.

Bulgaria signs a non-aggression pact with Greece and other states of Balkan Antanti (Turkey, Romania, Yugoslavia).

Treaty of Craiova: Romania loses Southern Dobrudja to Bulgaria.

World War II: Bulgaria signs the Tripartite Pact, allying itself with the Axis powers.

World War II: First German military units enter Bulgaria after it joined the Axis Pact.

World War II: UK declares war on Bulgaria. Hungary and Romania declare war on the United States. India declares war on Japan.

World War II: United States declares war on Bulgaria, Hungary, and Romania.

World War II: The Fatherland Front takes power in Bulgaria through a military coup in the capital and armed rebellion in the country. A new pro-Soviet government is established.

Albania, Austria, Bulgaria, Cambodia, Finland, Hungary, Ireland, Italy, Jordan, Laos, Libya, Nepal, Portugal, Romania, Spain and Sri Lanka join the United Nations.

While walking across Waterloo Bridge in London, Bulgarian dissident Georgi Markov is assassinated by Bulgarian secret police agent Francesco Giullino by means of a ricin pellet fired from a specially-designed umbrella.

While walking across Waterloo Bridge in London, Bulgarian dissident Georgi Markov is assassinated by Bulgarian secret police agent Francesco Giullino by means of a ricin pellet fired from a specially-designed umbrella.

Fall of the communist regime in Bulgaria.

While ''en route'' from Adana to Ankara, a Turkish Airlines flight with a crew of 6 and 33 passengers is hijacked by a Kurdish militant who orders the pilot to fly to Switzerland. The plane instead lands in Ankara after the pilot tricked the hijacker into thinking that he is landing in the Bulgarian capital of Sofia to refuel.

Simeon Saxe-Coburg-Gotha, the last Tsar of Bulgaria when he was a child, is sworn in as Prime Minister of Bulgaria, becoming the first monarch in history to regain political power through democratic election to a different office.

Bulgaria, Cyprus, Latvia, Malta, Slovenia and Slovakia join the European Environment Agency.

NATO invites Bulgaria, Estonia, Latvia, Lithuania, Romania, Slovakia and Slovenia to become members.

Bulgaria, Estonia, Latvia, Lithuania, Romania, Slovakia and Slovenia join NATO as full members.

Bulgaria and Romania sign accession treaties to join the European Union.

Bulgaria and Romania officially join the European Union. Also, Bulgarian, Romanian, and Irish become official languages of the European Union, joining 20 other official languages.