August 27 is the 239th day of the year (240th in leap years) in the Gregorian calendar; 126 days remain until the end of the year.
410 – The sacking of Rome by the Visigoths ends after three days.
1172 – Henry the Young King and Margaret of France are crowned junior king and queen of England.
1593 – Pierre Barrière failed an attempt to assassinate Henry IV of France.
1776 – American Revolutionary War: Members of the 1st Maryland Regiment repeatedly charged a numerically superior British force during the Battle of Long Island, allowing General Washington and the rest of the American troops to escape.
1798 – Wolfe Tone's United Irish and French forces clash with the British Army in the Battle of Castlebar, part of the Irish Rebellion of 1798, resulting in the creation of the French puppet Republic of Connacht.
1810 – Napoleonic Wars: The French Navy defeats the British Royal Navy, preventing them from taking the harbour of Grand Port on Île de France.
1813 – French Emperor Napoleon I defeats a larger force of Austrians, Russians, and Prussians at the Battle of Dresden.
1832 – Black Hawk, leader of the Sauk tribe of Native Americans, surrenders to U.S. authorities, ending the Black Hawk War.
1859 – Petroleum is discovered in Titusville, Pennsylvania, leading to the world's first commercially successful oil well.
1881 – The Georgia hurricane makes landfall near Savannah, Georgia, resulting in an estimated 700 deaths.
1883 – Eruption of Krakatoa: Four enormous explosions almost completely destroy the island of Krakatoa and cause years of climate change.
1893 – The Sea Islands hurricane strikes the United States near Savannah, Georgia, killing between 1,000 and 2,000 people.
1896 – Anglo-Zanzibar War: The shortest war in world history (09:02 to 09:40), between the United Kingdom and Zanzibar.
1914 – World War I: Battle of Étreux: A British rearguard action by the Royal Munster Fusiliers during the Great Retreat.
1914 – World War I: Siege of Tsingtao: A Japanese fleet commanded by Vice Admiral Sadakichi Kato imposes a blockade along the whole coastline of German Tsingtao, initiating the Siege of Tsingtao.
1916 – World War I: The Kingdom of Romania declares war on Austria-Hungary, entering the war as one of the Allied nations.
1918 – Mexican Revolution: Battle of Ambos Nogales: U.S. Army forces skirmish against Mexican Carrancistas in the only battle of World War I fought on American soil.
1943 – World War II: Aerial bombardment by the Luftwaffe razes to the ground the village of Vorizia in Crete.