| 17 October 1346 | England, Scotland, France [Anglo–Scottish Wars 1296–1371)] | King David II of Scotland invades England and is defeated and captured at Neville's Cross, outside Durham, England. His action helps to relieve the pressure placed on France by King Edward III of England. |
| 17 October 1404 | Papal States [administration] | Cosmo Migliorato is elected Pope Innocent VII in Rome. |
| 17 October 1448 | Hungary, Ottoman Empire [wars] | The Ottoman sultan Murad II defeats János Hunyadi, Voivode (governor) of Transylvania, at the second Battle of Kosovo Polje in Serbia and thus regains control of the Balkans, excluding Albania. |
| 17 October 1472 | Aragon, Spain [diplomacy] | Barcelona, Catalonia, surrenders on compromise terms to King John II of Aragon. The secessionist revolt of Catalonia under its Generalitat (parliament) ends, and Catalonia and Aragon are united when they face King Louis XI of France in Roussillon, France. |
| 17 October 1604 | UK [health and medicine] | King James I writes his Counterblast to Tobacco, condemning the increasingly popular habit of smoking in Britain. It is published anonymously. He also imposes a heavy duty on the importing of tobacco. |
| 17 October 1605 | Mogul Empire [births and deaths] | Akbar, Mogul emperor of India 1556–1605, who brought most of India under Mogul rule, dies in Agra, India (c. 63). |
| 17 October 1725 | England [births and deaths] | John Wilkes, outspoken English journalist and politician who championed radical principles of political and civil liberty, born in London, England (–1797). |
| 17 October 1726 | Habsburg Monarchy, Prussia [treaties] | By the Treaty of Wusterhausen with the Habsburg Monarchy, Prussia leaves the alliance of Herrenhausen (of 23 August 1725) and guarantees the Pragmatic Sanction, which sets out the right of Maria Theresa of Austria to succeed her father, the Holy Roman Emperor Charles VI, as ruler of all the Habsburg domains. Prussia undertakes to aid Austria with 10,000 troops in any resulting war. |
| 17 October 1760 | Britain [political events] | Following the death of King George II of Britain, he is succeeded by his grandson George III, aged 22. |
| 17 October 1797 | France, Austria-HM, Italy, Venice, Belgium, Greece-Ottoman, Germany [treaties] | The Treaty of Campo Formio is signed by France and Austria after Napoleon Bonaparte's successful campaign in Italy and Tyrol. The Cisalpine and Ligurian republics are recognized, as is French possession of the Ionian Islands off the Greek coast. Austria occupies the Venetian lands east of the River Adige, including Istria, Dalmatia, and Venice, and cedes the Austrian Netherlands to France. Peace between the Holy Roman Empire and France is to be negotiated at a conference to be held at Rastatt, Germany. |
| 17 October 1849 | France [births and deaths] | Frédéric Chopin, French composer known for his works for piano, dies in Paris, France (39). |
| 17 October 1854 | UK, France, Russian Empire [Crimean War (1854–56)] | English and French forces begin the siege of the Russian-held city of Sevastopol in the Crimea. |
| 17 October 1860 | UK [golf] | A 3-round 36-hole strokeplay competition for professional golfers at Prestwick, Scotland, regarded as the first British Open golf championship, is won by Scottish golfer Willie Park, Sr. |
| 17 October 1900 | Germany [administration] | Bernhard von Bülow succeeds the aged Prince Chlodwig von Hohenlohe as the German chancellor. |
| 17 October 1927 | Norway [political events] | The first Labour government is formed in Norway by Christopher Hornsrud, following a general election in which Labour won 59 seats, the Conservatives 30, the Liberals 30, and the Farmers' Party 26. |
| 17 October 1973 | Middle East, USA, Israel [Yom Kippur War (1973)] | Eleven Arab states agree to cut their oil production by 5% a month in protest against US support for Israel in the Middle East Yom Kippur War. |
| 17 October 1989 | USA [natural disasters] | An earthquake measuring 7.1 on the Richter scale hits San Francisco, California, killing at least 273 people, many of whom die when the upper level of the Nimitz Highway collapses. It is North America's most destructive earthquake since 1906, causing at least $6 billion in property damage. |
| 17 October 1996 | USA [health and medicine] | US researchers from the University of Texas and the Beckman Research Institute based in Hope, California, announce the discovery that cigarette smoke alters a gene which suppresses the uncontrolled growth of cells that cause tumours. It is the first direct evidence for the statistical link between cigarette smoking and cancer. |
