| 15 September 1485 | Poland-Lithuania, Moldavia, Holy Roman Empire, Ottoman Empire [wars] | During a campaign against the Ottoman and Tatar forces advancing along the Black Sea coast, King Casimir (Kazimierz) IV of Poland receives the homage of the voivod of Moldavia, Stephen III the Great. |
| 15 September–5 December 1590 | Papal States, Italy [political events] | Giovanni Battista Castagna is elected as Pope Urban VII, Succeeding Sixtus V who died exactly a month earlier. Pope Urban VII, however, dies after only 13 days in office, and is succeeded in turn by Niccolo Sfondrati on 5 December. |
| 15 September 1644 | Papal States, Italy [political events] | Giovanni Battista Pamfili is elected Pope Innocent X in succession to Urban VIII. |
| 15 September 1789 | USA [births and deaths] | James Fenimore Cooper, US novelist who wrote of life on the frontier, born in Burlington, New Jersey (–1851). |
| 15 September 1789 | France [births and deaths] | Louis Daguerre, French painter and physicist who invented the first practical method of photography, the daguerreotype, born in Cormeilles, near Paris, France (–1851). |
| 15 September 1821 | Guatemala, Spain, Mexico [decolonization] | Guatemala declares itself independent of Spain and aligns itself with Mexico. |
| 15 September 1830 | UK, USA [railways] | The Liverpool and Manchester Railway opens in England. The first railway to carry both passengers and freight, its success sparks widespread railway building in Britain and the USA. |
| 15 September 1859 | England [births and deaths] | Isambard Kingdom Brunel, British marine engineer who built the first transatlantic steamer, the Great Western (1838), and the Great Eastern (1858), the largest ship in the world for 40 years, dies in Westminster, London, England (53). |
| 15 September 1910 | South Africa [elections] | The South African Party wins the first South African elections and Louis Botha becomes prime minister. |
| 15 September–24 November 1914 | Europe [World War I (1914–18)] | The ‘race to the sea’ takes place as Allied and German forces move northwards trying to outflank one other. This establishes the basic line of the Western Front, stretching from the North Sea through Belgium and France to Switzerland. |
| 15–24 September 1918 | Serbia [World War I (1914–18)] | An Allied (French, British, Italian, and Serbian) offensive makes large gains at the Battle of Monastir on the Macedonian front. |
| 15 September 1935 | Germany [political events] | The German Führer Adolf Hitler announces the racist ‘Nuremberg Laws’ against Jews at the Nazi Party Nuremberg rally. Legislation will define Jews, ban them from professions, and forbid their marriage or sexual relations with non-Jews. |
| 15 September 1937 | USA [legislation] | The National Housing Act (Wagner–Steagall Act) creates the US Housing Authority, to make housing for people on low incomes more affordable and to spur rural and urban construction. |
| 15 September 1943 | Italy [World War II (1939–45)] | The former Italian prime minister Benito Mussolini establishes a new republican fascist government at Salò on Lake Garda, Italy. |
| 15 September 1972 | South Vietnam, North Vietnam [Vietnam War (1954–75)] | South Vietnamese forces recapture the city of Quang Tri from the North Vietnamese. |
| 15 September 1978 | Spain [law and government] | The Spanish parliament recognizes the demand of the Basques for autonomy. |
| 15 September 2006 | Germany [Catholicism] | Pope Benedict XVI, the head of the Roman Catholic Church, delivers a lecture in Germany which includes a reference to a critical medieval text on Islam, provoking worldwide Muslim protests. The Vatican apologises for any unintentional offence. |
