27 April

395 – Emperor Arcadius marries Aelia Eudoxia, daughter of the Frankish general Flavius Bauto. She becomes one of the more powerful Roman empresses of Late Antiquity.
1296 – First War of Scottish Independence: John Balliol's Scots army is defeated by an English army commanded by John de Warenne, 6th Earl of Surrey at the Battle of Dunbar.
1509 – Pope Julius II places the Italian state of Venice under interdict.
1521 – Battle of Mactan: Explorer Ferdinand Magellan is killed by natives in the Philippines led by chief Lapu-Lapu.
1522 – Combined forces of Spain and the Papal States defeat a French and Venetian army at the Battle of Bicocca.
1539 – Re-founding of the city of Bogotá, New Granada (now Colombia), by Nikolaus Federmann and Sebastián de Belalcázar.
1565 – Cebu is established becoming the first Spanish settlement in the Philippines.
1578 – Duel of the Mignons claims the lives of two favourites of Henry III of France and two favorites of Henry I, Duke of Guise.
1650 – The Battle of Carbisdale: A Royalist army from Orkney invades mainland Scotland but is defeated by a Covenanter army.
1667 – The blind and impoverished John Milton sells the copyright of Paradise Lost for £10.
1749 – First performance of Handel's Music for the Royal Fireworks in Green Park, London.
1777 – American Revolutionary War: The Battle of Ridgefield: A British invasion force engages and defeats Continental Army regulars and militia irregulars at Ridgefield, Connecticut.
1805 – First Barbary War: United States Marines and Berbers attack the Tripolitan city of Derna (The "shores of Tripoli" part of the Marines' hymn).
1810 – Beethoven composes Für Elise.
1813 – War of 1812: United States troops capture the capital of Upper Canada in the Battle of York (present day Toronto, Canada).
1840 – Foundation stone for new Palace of Westminster, London, is laid by wife of Sir Charles Barry.
1861 – President of the United States Abraham Lincoln suspends the writ of habeas corpus.
1865 – The New York State Senate creates Cornell University as the state's land grant institution.
1865 – The steamboat SS Sultana, carrying 2,400 passengers, explodes and sinks in the Mississippi River, killing 1,700, most of whom are Union survivors of the Andersonville and Cahaba Prisons.
1904 – The Australian Labor Party becomes the first such party to gain national government, under Chris Watson.
1909 – Sultan of Ottoman Empire Abdul Hamid II is overthrown, and is succeeded by his brother, Mehmed V.
1911 – Following the resignation and death of William P. Frye, a compromise is reached to rotate the office of President pro tempore of the United States Senate.
1914 – Honduras becomes a signatory to the Buenos Aires copyright treaty.
1927 – Carabineros de Chile (Chilean national police force and gendarmery) are created.
1936 – The United Auto Workers (UAW) gains autonomy from the American Federation of Labor.
1941 – World War II: German troops enter Athens.
1941 – World War II: The Communist Party of Slovenia, the Slovene Christian Socialists, the left-wing Slovene Sokols (also known as "National Democrats") and a group of progressive intellectuals establish the Liberation Front of the Slovenian People.
1945 – World War II: German troops are finally expelled from Finnish Lapland.
1945 – World War II: Benito Mussolini is arrested by Italian partisans in Dongo, while attempting escape disguised as a German soldier.
1950 – Apartheid: In South Africa, the Group Areas Act is passed formally segregating races.
1953 – Operation Moolah is initiated by General Mark W. Clark against Communist pilots.
1960 – Togo gains independence from French-administered UN trusteeship.
1961 – Sierra Leone is granted its independence from the United Kingdom, with Milton Margai as the first Prime Minister.
1967 – Expo 67 officially opens in Montreal, Canada with a large opening ceremony broadcast around the world. It opens to the public the next day.
1974 – 10,000 march in Washington, D.C., calling for the impeachment of US President Richard Nixon
1977 – 28 people are killed in the Guatemala City air disaster.
1978 – Former United States President Nixon aide John D. Ehrlichman is released from an Arizona prison after serving 18 months for Watergate-related crimes.
1981 – Xerox PARC introduces the computer mouse.
1987 – The U.S. Department of Justice bars the Austrian President Kurt Waldheim from entering the United States, saying he had aided in the deportation and execution of thousands of Jews and others as a German Army officer during World War II.
1992 – The Federal Republic of Yugoslavia, comprising Serbia and Montenegro, is proclaimed.
1992 – Betty Boothroyd becomes the first woman to be elected Speaker of the British House of Commons in its 700-year history.
1992 – Russia and 12 other former Soviet republics become members of the International Monetary Fund and the World Bank.
1993 – All members of the Zambia national football team lose their lives in a plane crash off Libreville, Gabon in route to Dakar, Senegal to play a 1994 FIFA World Cup qualifying match against Senegal.
1994 – South African general election, 1994: The first democratic general election in South Africa, in which black citizens could vote. The Interim Constitution comes into force.
1996 – The 1996 Lebanon war ends.
2002 – The last successful telemetry from the NASA space probe Pioneer 10.
2005 – The superjumbo jet aircraft Airbus A380 makes its first flight from Toulouse, France.
2006 – Construction begins on the Freedom Tower for the new World Trade Center in New York City.
2007 – Estonian authorities remove the Bronze Soldier, a Soviet Red Army war memorial in Tallinn, amid political controversy with Russia.
2011 – The 2011 Super Outbreak of tornadoes devastates parts of the southeastern United States, especially the State of Alabama, killing nearly 300.

Holidays and observances

Christian Feast Day:
Liberalis of Treviso
Virgin of Montserrat
Zita
April 27 (Eastern Orthodox liturgics)
Day of the Uprising Against the Occupying Forces (Slovenia)
Freedom Day (South Africa), and its related observances:
UnFreedom Day (South Africa, unofficial)
Independence Day, celebrates the independence of Sierra Leone from United Kingdom in 1961.
Independence Day, celebrates the independence of Togo from France in 1960.
National War Veterans' Day (Finland)
World Tapir Day, raises awareness of threatened tapir species