| 23 April 1014 | Ireland [births and deaths] | Brian Bórumha, high king of Ireland 1002–14, is killed at the Battle of Clontarf, near Dublin, Ireland (c. 73). |
| 23 April 1016 | England [political events] | Edmund Ironside succeeds to the English throne following the death of his father, King Aethelred II the Unready of England. Edmund revitalizes English resistance to Cnut, the Danish claimant to the English throne. |
| 23 April 1616 | England [births and deaths] | William Shakespeare, English dramatist and poet, often considered the greatest playwright in history, dies in Stratford-upon-Avon, Warwickshire, England (52). |
| 23 April–4 May 1702 | UK, United Netherlands, Austria, Habsburg Monarchy, Holy Roman Empire, France [War of the Spanish Succession (1701–1714)] | Britain, the United Netherlands, and Austria declare war on France, marking the formal opening of the War of the Spanish Succession. |
| 23 April 1850 | England [births and deaths] | William Wordsworth, English Romantic poet, and poet laureate 1843–50, dies in Grasmere, Westmorland, England (80). |
| 23 April 1858 | Germany [births and deaths] | Max Planck, German theoretical physicist who is the originator of quantum theory, born in Kiel, in the duchy of Schleswig (–1947). |
| 23 April 1904 | USA, Panama [companies and organizations] | The USA acquires the property of the French Panama Canal Company when the Panama Canal zone is transferred at a meeting in Paris, France. |
| 23 April 1920 | Anatolia [law and government] | A new Turkish assembly opens at Ankara, Anatolia (modern Turkey), which elects the nationalist Mustafa Kemal as its president and proclaims a new constitution, the Law of Fundamental Organization. |
| 23 April 1921 | Romania [political events] | Through a Czechoslovak-Romanian alliance Romania joins the ‘Little Entente’ (a defensive alliance of eastern European nations). |
| 23–30 April 1942 | UK, Germany [World War II (1939–45)] | In the Baedeker raids, named after the German tourist guidebooks, German aircraft bomb Exeter, Bath, and other historic cities in Britain in reprisal for British raids on Cologne and Lübeck. |
| 23 April 1988 | USA [social legislation] | The US government bans smoking on all internal passenger airline flights of under two hours' duration. |
| 23 April 1992 | UK [everyday life] | Princess Anne, the Princess Royal of Britain, is granted a divorce from Captain Mark Phillips. |
| 23 April 1998 | UK [literature and language] | The British publishing and bookseller industries launch World Book Day with events and celebrations; all schoolchildren in the country receive a £1 book token. |
| 23 April 1998 | USA [births and deaths] | James Earl Ray, US gunman who pleaded guilty to the 1968 assassination of black civil rights leader Martin Luther King JR, dies in prison in Nashville, Tennessee (70). |
| 23 April 1998 | England [information technology] | The first cash machines to use ‘iris recognition technology’ to identify the user and dispense money, enter service in Swindon, England. |
