| 17 May 1186 | Papal States, Italy, Holy Roman Empire [Christianity] | Pope Urban III causes a break with the Holy Roman Emperor Frederick I Barbarossa by consecrating the papal candidate for the archbishopric of Trier despite having sworn earlier that he would not do this. |
| 17 May 1257 | Holy Roman Empire, Germany [political events] | Richard, Earl of Cornwall, is crowned King of the Romans in Aachen, Germany. |
| 17 May 1395 | Hungary, Wallachia, Ottoman Empire [wars] | The Hungarians and Wallachians defeat the Ottoman Turks at Rovine, but Wallachia becomes tributary to the Turks, who also conquer the Dobrudja area of the Balkans. |
| 17 May 1510 | Florence [births and deaths] | Sandro Botticelli (original name Alessandro di Mariano Filipepi), Florentine painter of the early Renaissance, whose major works include The Birth of Venus (c. 1484) and Primavera/Spring (c. 1478), dies in Florence, Italy (c. 65). |
| 17–19 May 1606 | Russia [political events] | The Russian tsar, the ‘false Dmitri’, is murdered in another Moscow uprising, sponsored by his erstwhile backer Vasily Shuysky returning from a banishment promoted by Dmitri's Polish wife Marina Mniszek. Shuysky usurps the throne; he gains the support of his fellow boyars (nobles) by promising rule through a duma (parliament) and is proclaimed Tsar Vasily IV on 19 May. |
| 17 May 1648 | Sweden, France, Bavaria, Germany, Holy Roman Empire [Thirty Years War (1618–48)] | Swedish and French forces, under Karl Gustaf Wrangel and Marshal Turenne, defeat a Bavarian-imperial army at the Battle of Zusmarshausen, near Augsburg. Bavaria is overrun once again. |
| 17 May 1727 | Russia [births and deaths] | Catherine I (original name Marta Skowronska), ruling empress of Russia 1725–27, wife of Peter I the Great of Russia, dies in St Petersburg, Russia (43). |
| 17 May 1727 | Russia [political events] | The young Grand Duke Peter Alexeyvich (Tsar Peter II), son of the murdered Tsarevich Alexey Petrovich, is named by Catherine I, empress of Russia, as her successor, with the entire Supreme Privy Council to act as regents. |
| 17 May 1749 | England [births and deaths] | Edward Jenner, English surgeon who discovered and developed a smallpox vaccination, born in Berkeley, Gloucestershire, England (–1823). |
| 17 May 1756 | Habsburg Monarchy, Holy Roman Empire, UK, France [Seven Years War (1754–62)] | Following the Diplomatic Revolution of 1 May, which created two opposing power blocs in Europe (Austria, France, Russia, Sweden, and Saxony opposed to Prussia, Great Britain, and Portugal), Britain formally declares war on France (the challenge is accepted on 9 June). |
| 17 May 1782 | India [treaties] | After a British defeat at Wadgaon, India, in January 1779 and largely inconclusive warfare since, the Treaty of Salbai ends the first Anglo-Maratha war with minimal British gains. |
| 17 May 1809 | Papal States, France [political events] | The French emperor Napoleon I issues an imperial decree annexing the Papal States, following their occupation by France in February 1808. |
| 17 May 1885 | Pacific, Germany [colonization] | Germany annexes Northern New Guinea and the Bismarck Archipelago. |
| 17–18 May 1900 | South Africa [Anglo–Boer Wars (1899–1902)] | British forces under General Sir Redvers Buller relieve the town of Mafeking, southern Africa, following a seven-month siege by a Boer force. |
| 17 May 1989 | Poland [Catholicism] | The Roman Catholic Church in Poland is given a status unparalleled in post-war Eastern Europe, with the restoration of property confiscated in the 1950s and the right to run schools. |
