| 121921 | October 24 | Holiday and observance | World Polio Day (International) |
| 121922 | October 25 | Event | 473 – Emperor Leo I acclaims his grandson Leo II as Caesar of the Byzantine Empire. |
| 121923 | October 25 | Event | 1147 – Seljuk Turks defeat German crusaders under Conrad III at the Battle of Dorylaeum. |
| 121924 | October 25 | Event | 1147 – Reconquista: After a siege of four months, crusader knights led by Afonso Henriques reconquered Lisbon |
| 121925 | October 25 | Event | 1415 – Hundred Years' War: Henry V of England and his lightly armoured infantry and archers defeat the heavily armoured French cavalry in the Battle of Agincourt on Saint Crispin's Day. |
| 121926 | October 25 | Event | 1616 – Dutch sea-captain Dirk Hartog makes second recorded landfall by a European on Australian soil, at the later-named Dirk Hartog Island off the West Australian coast. |
| 121927 | October 25 | Event | 1712 – coronation de Louis XV of France |
| 121928 | October 25 | Event | 1747 – British fleet under Admiral Sir Edward Hawke defeats the French at the Second Battle of Cape Finisterre. |
| 121929 | October 25 | Event | 1760 – George III becomes King of Great Britain. |
| 121930 | October 25 | Event | 1812 – War of 1812: The American frigate, USS United States, commanded by Stephen Decatur, captures the British frigate HMS Macedonian. |
| 121931 | October 25 | Event | 1822 – Greek War of Independence: The First Siege of Missolonghi begins. |
| 121932 | October 25 | Event | 1828 – St Katharine Docks open in London. |
| 121933 | October 25 | Event | 1854 – The Battle of Balaclava during the Crimean War (Charge of the Light Brigade). |
| 121934 | October 25 | Event | 1861 – The Toronto Stock Exchange is created. |
| 121935 | October 25 | Event | 1900 – The United Kingdom annexes the Transvaal. |
| 121936 | October 25 | Event | 1917 – Traditionally understood date of the October Revolution, involving the capture of the Winter Palace, Petrograd, Russia. The date refers to the Julian Calendar date, and corresponds with November 7 in the Gregorian calendar. |
| 121937 | October 25 | Event | 1920 – After 74 days on hunger strike in Brixton Prison, England, the Sinn Féin Lord Mayor of Cork, Terence MacSwiney dies. |
| 121938 | October 25 | Event | 1924 – The Zinoviev letter, which Zinoviev himself denied writing, is published in the Daily Mail. The Labour party would later blame this letter for the Conservatives' landslide election win. |
| 121939 | October 25 | Event | 1927 – The Italian luxury liner SS Principessa Mafalda sinks off the coast of Brazil, killing 314. |
| 121940 | October 25 | Event | 1938 – The Archbishop of Dubuque, Francis J. L. Beckman, denounces swing music as "a degenerated musical system… turned loose to gnaw away at the moral fiber of young people", warning that it leads down a "primrose path to hell". His warning is widely ign |
| 121941 | October 25 | Event | 1940 – Benjamin O. Davis, Sr. is named the first African American general in the United States Army. |
| 121942 | October 25 | Event | 1944 – Heinrich Himmler orders a crackdown on the Edelweiss Pirates, a loosely organized youth culture in Nazi Germany that had assisted army deserters and others to hide from the Third Reich. |
| 121943 | October 25 | Event | 1944 – The USS Tang under Richard O'Kane (the top American submarine captain of World War II) is sunk by the ship's own malfunctioning torpedo. |
| 121944 | October 25 | Event | 1944 – The Romanian city of Carei is liberated by Romanian and Soviet forces from Nazi-Hungarian occupation. |
| 121945 | October 25 | Event | 1944 – World War II: Battle of Leyte Gulf: The largest naval battle in history, takes place in and around the Philippines between the Imperial Japanese Navy and the U.S. Third and U.S. Seventh Fleets. Afterward is the first Kamikaze attack of the war. |
| 121946 | October 25 | Event | 1945 – The Republic of China takes over administration of Taiwan following Japan's surrender to the Allies. |
| 121947 | October 25 | Event | 1962 – Cuban Missile Crisis: Adlai Stevenson shows photos at a meeting of the United Nations Security Council proving that Soviet missiles are installed in Cuba. |
| 121948 | October 25 | Event | 1962 – Uganda joins the United Nations. |
| 121949 | October 25 | Event | 1962 – Nelson Mandela is sentenced to five years in prison. |
| 121950 | October 25 | Event | 1971 – The United Nations seats the People's Republic of China and expels the Republic of China (see political status of Taiwan and China and the United Nations) |