| 12 May 1012 | Italy, Holy Roman Empire [political events] | The death of Pope Sergius IV within a few weeks of that of his patron John II Crescentius leads to suspicions that they have both been murdered. The election of Sergius IV's successor is disputed: the Crescentius family nominate Gregory, but he is soon expelled by the counts of Tusculum, who put Theophylact of Tusculum, as Benedict VIII, in possession of the papacy. |
| 12 May 1182 | Denmark, Holy Roman Empire [administration] | Following the death of King Valdemar I the Great of Denmark, he is succeeded by his son Cnut IV, who refuses to do homage to the Holy Roman Emperor Frederick I Barbarossa. |
| 12 May 1194 | England, France [taxation] | Having raised money by the sale of charters and a new tax called the Carucage (based on the Danegeld), King Richard I the Lionheart leaves England to re-establish his authority in his French lands. |
| 12 May 1495 | Italy, France [political events] | King Charles VIII of France is crowned king of Naples, but faced with a counteroffensive from the League of Venice, leaves for France a fortnight later. |
| 12 May 1534 | Germany, Austria, Habsburg Monarchy, Holy Roman Empire, Württemberg [political events] | Philip, Landgrave of Hesse, leads the German Protestant Schmalkaldic League, aided by Bavaria, in defeating the army of Ferdinand I, Archduke of Austria, at Lauffen to restore the Protestant convert Ulrich as Duke of Württemberg. |
| 12 May 1809 | UK, France, Portugal [Napoleonic Wars (1803–15)] | British forces under Arthur Wellesley (later Duke of Wellington) defeat the French under Marshal Nicolas-Jean Soult at Oporto and force them to retreat from Portugal. |
| 12 May 1820 | England, Florence [births and deaths] | Florence Nightingale, ‘Lady of the Lamp’, English nurse who is in charge of nursing the British troops during the Crimean War and who establishes nursing as a profession for women, born in Florence, Italy (–1910). |
| 12 May 1823 | UK [Catholicism] | The Catholic Association is established in Ireland by the nationalist Daniel O'Connell to agitate for Catholic Emancipation (the removal of legal restrictions on Catholics) and independence. |
| 12 May 1870 | Canada [political events] | Manitoba is made a Canadian province, which helps to end the Red River Rebellion by mixed-blood rebels over territory. |
| 12 May 1888 | Netherlands East Indies, UK [colonization] | The British proclaim a protectorate in North Borneo and Brunei. |
| 12 May 1922 | USA [astronomy] | A 20.3 tonne/20 ton meteorite lands in a field near Blackstone, Virginia, leaving a 46 sq m/500 sq ft hole in the ground. |
| 12 May 1928 | Italy [suffrage] | An Italian law abolishes female suffrage, reduces the electorate from 10 million to 3 million, and arranges for 400 government candidates to be accepted or rejected en bloc. |
| 12 May 1937 | UK [television] | The televising of the Coronation by the British Broadcasting Corporation (BBC) is the first major outside broadcast in Britain and viewed by an estimated 50,000 people. |
| 12 May 1962 | Laos [diplomacy] | Negotiations are held in Laos between the leaders of the three warring parties, who reach agreement. A Provisional Government of National Unity is established on 22 May, with Prince Souvanna Phouma as president. |
| 12 May 1992 | USA [Protestantism] | The General Conference of the United Methodist Church declares that homosexual behaviour conflicts with Christian teachings. |
| 12 May 1999 | UK [political events] | The new Scottish Parliament comes into existence in Edinburgh. It is Scotland's first parliament for nearly 300 years. |
| 12 May 2000 | UK [museums and galleries] | The Tate Modern art gallery opens at Bankside, London, England. |
| 12 May 2003 | Saudi Arabia [terrorism] | Suicide bombers in the Saudi Arabian capital of Riyadh target three compounds housing Western expatriate workers and their families, killing at least 34 people including themselves. About 190 are injured. The operation is believed to have been planned and executed by the al-Qaeda international terrorist network. |
| 12–14 May 2003 | Russia [terrorism] | In two terrorist incidents in Russia's troubled republic of Chechnya, suicide bombers believed to be Chechen separatists target a government security service building and, two days later, attempt to kill the Moscow-backed head of the Chechen administration at a Muslim festival. Around 80 people are believed killed in the attacks. |
