| 26 June 1243 | Mongol Empire, Seljuk Sultanate of Rum, Georgia [Mongol conquests (1206–1405)] | The Mongols defeat Kay-Khusraw II, Sultan of Rum, and his Byzantine allies at Köse Dagh, near Erzinjan; he becomes their tributary, as does Queen Rusadan of Georgia. |
| 26 June–17 July 1245 | Italy, France, Holy Roman Empire [political events] | Pope Innocent IV holds the General Council in Lyons, France. It legislates for reform, calls for new crusades to liberate Jerusalem, and culminates with Innocent's declaration of the Holy Roman Emperor Frederick II's deposition and invitation to the German nobles to elect a new king. |
| 26 June 1409 | Italy [administration] | The cardinals meeting in Pisa elect Cardinal Peter Philarges as the antipope Alexander V. |
| 26 June–16 July 1519 | Holy Roman Empire, Germany, Saxony [Catholicism] | The German Catholic theologian Johann Eck debates grace, free will, the primacy of the pope, and the infallibility of the general council, with the German church reformer Martin Luther and the more radical German reformer Andreas Carlstadt, in a public disputation at Leipzig, in the Electorate of Saxony. |
| 26 June 1529 | Swiss Confederation [political events] | The first Peace of Kappel ends desultory hostilities in the Swiss Confederation between the Catholic cantons of the Christian Union and those of the Protestant Civic League, led by the Zürich of Ulrich Zwingli. The Union agrees to break its alliance with Habsburg Austria, and both sides agree to freedom of conscience in the common subject areas. |
| 26 June 1718 | Russia [political events] | Tsarevich Aleksey Petrovich, heir to Tsar Peter I the Great of Russia and focus for opposition to the Tsar's sweeping economic and social reforms, dies (or is put to death) in St Petersburg, aged 28, after repeated interrogation under torture. |
| 26 June–2 July 1767 | America [legislation] | The British Parliament adopts the Townshend Acts, taxing all glass, lead, paper, paints, and tea imported to the American colonies. To ensure compliance, the acts establish a Board of Customs Commissioners in Boston, a city becoming notorious for its recalcitrance. |
| 26 June 1794 | Austria-HM, France, Austrian Netherlands, Belgium [French Revolutionary Wars (1792–1801)] | A French army under General Jean-Baptiste Jourdan defeats Austrian forces at Fleurus in the Austrian Netherlands. The Austrian commander, Freidrich Josias, Prince of Saxe-Coburg, evacuates the Austrian Netherlands. |
| 26 June 1810 | France [births and deaths] | Joseph-Michel Montgolfier, French aeronaut who, with his brother Jacques-Etienne, developed the hot-air balloon, dies in Balaruc-les-bains, France (69). |
| 26 June 1824 | Scotland, Northern Ireland [births and deaths] | William Thomson (Lord Kelvin), Scottish physicist who developed the absolute temperature scale, born in Belfast, Ireland (–1907). |
| 26 June 1830 | England [political events] | Following the death of King George IV of Britain, he is succeeded by his brother William IV, duke of Clarence. |
| 26 June 1846 | UK [taxation] | The British prime minister, Robert Peel, repeals the Corn Laws to allow the unhindered importation of grain into Ireland in an effort to alleviate the famine caused there by the failure of the potato crop. His Conservative Party wants to retain the Corn Laws to protect the position of the landed elite and splits over the issue. |
| 26 June 1858 | UK, China, France [treaties] | The Treaty of Tianjin between China and Britain ends the Second Opium War, by which China opens more ports to British commerce and legalizes the opium trade. A similar treaty is signed between the Chinese and the French on 27 June. |
| 26–27 June 1906 | France, Austria-Hungary [motor-racing and rallying] | The Hungarian driver Ferenc Szisz, in a Renault, wins the French Grand Prix at Le Mans. This is regarded as the first ever motor-racing Grand Prix. |
| 26–28 June 1940 | USSR, Romania, Germany [diplomacy] | The USSR demands Bessarabia and Bukovina from Romania. Romania requests German support for rejection of the demand, but the German Führer refuses. Romania cedes the territories on 27 June and they are occupied by Soviet troops on 28 June. |
| 26 June 1960 | Madagascar [decolonization] | The French colony of Madagascar is proclaimed independent as the Malagasy Republic (but remains within the French Community). It is admitted to the United Nations (UN) on 20 September. |
| 26 June 1960 | British Somaliland, Somalia [decolonization] | British Somaliland becomes independent and, on 27 June, unites with Somalia. |
| 26 June 1974 | USA [technology] | The first product barcode (on a pack of Wrigley's chewing gum) is scanned at the checkout of the Marsh Supermarket in Troy, Ohio. |
| 26 June 1978 | South Yemen [political events] | The president of South Yemen, Salem Ruba Ali, is assassinated by the faction that murdered the North Yemeni president, Ahmed al-Ghashmi. |
| 26 June 1997 | [maths] | The English mathematician Andrew Wiles is awarded the Wolfskehl Prize for solving Fermat's last theorem. The most notorious problem in mathematics, the Last Theorem was created in the 17th century by the French judge Pierre de Fermat, who studied mathematics in his spare time. In 1908 the German industrialist Paul Wolfskehl bequeathed DM100,000 (£1 million by today's value) to be given to the first person to prove it. |
| 26 June 2000 | USA, UK [biology] | Scientists working on the Human Genome Project in London, England, and Washington, DC, announce that they have completed the first draft of the entire structure of human DNA. |
