This list includes 39 historical events beginning with O. They span from “O. K. Corral, Gunfight at the” to “Overthrow of the Kingdom of Hawaii”. Entries include battles, coups, legal rulings, and social movements useful for study, teaching, and quick reference.
[Historical events that start with O] are notable occurrences or turning points whose common English names begin with O. They include diverse examples such as the O.K. Corral gunfight and the Overthrow of the Kingdom of Hawaii.
Below you’ll find the table with Year, Location, and Significance.
Year: Shows the year or range when the event occurred, so you can place each item in chronological context quickly.
Location: Notes the city, region, or country where the event took place, helping you connect events to geographic context.
Significance: A concise 15–25 word summary explains why the event matters and how it shaped people or institutions.
Historical events that start with O
| Event | Year(s) | Location | Type |
|---|---|---|---|
| Oath of the Tennis Court | 1789 | Versailles, France | Political pledge |
| Occupation of Alcatraz | 1969–1971 | San Francisco, USA | Protest / Civil rights action |
| Occupation of Japan | 1945–1952 | Japan | Post-war military occupation |
| Occupation of the Ruhr | 1923–1925 | Ruhr Valley, Germany | Military occupation |
| October Crisis | 1970 | Quebec, Canada | Political crisis / Terrorism |
| October Manifesto | 1905 | Russian Empire | Political reform |
| October Revolution | 1917 | Russia | Revolution / Coup d’état |
| October War (Yom Kippur War) | 1973 | Middle East | War |
| O. K. Corral, Gunfight at the | 1881 | Tombstone, Arizona, USA | Gunfight |
| Oklahoma City bombing | 1995 | Oklahoma City, USA | Domestic terrorism / Bombing |
| Oldcastle’s Rebellion | 1414 | England | Uprising |
| Olympic Games, Ancient, Founding of | 776 BC (traditional) | Olympia, Greece | Cultural / Sporting event |
| Olympic Games, Modern, Revival of | 1896 | Athens, Greece | Cultural / Sporting event |
| Onin War | 1467–1477 | Japan | Civil war |
| Opening of Japan | 1853–1854 | Japan | Diplomatic / Political event |
| Operation Barbarossa | 1941 | Eastern Europe / Soviet Union | Military invasion |
| Operation Desert Storm | 1991 | Iraq / Kuwait / Saudi Arabia | Military campaign |
| Operation Eagle Claw | 1980 | Iran | Military rescue mission |
| Operation Enduring Freedom | 2001–2014 | Afghanistan | Military operation / War |
| Operation Iraqi Freedom | 2003–2011 | Iraq | Military invasion / War |
| Operation Market Garden | 1944 | Netherlands | Military operation |
| Operation Mincemeat | 1943 | Europe | Military deception |
| Operation Overlord | 1944 | Normandy, France | Military invasion |
| Operation Paperclip | 1945–1959 | Germany / USA | Intelligence program |
| Operation Rolling Thunder | 1965–1968 | North Vietnam | Aerial bombing campaign |
| Operation Sea Lion | 1940 | English Channel / UK | Planned military invasion |
| Operation Torch | 1942 | North Africa | Military invasion |
| Opium War, First | 1839–1842 | China | War |
| Opium War, Second | 1856–1860 | China | War |
| Oprichnina | 1565–1572 | Russia | State policy / Reign of terror |
| Orange Revolution | 2004–2005 | Ukraine | Political protest / Revolution |
| Oregon Trail, Opening of the | c. 1841–1869 | Western United States | Mass migration / Expansion |
| Orgreave, Battle of | 1984 | Orgreave, South Yorkshire, UK | Civil unrest / Riot |
| Orléans, Siege of | 1428–1429 | Orléans, France | Siege / Battle |
| Orphan Train Movement | 1854–1929 | United States | Social welfare program |
| Ostend Manifesto | 1854 | Ostend, Belgium | Political document |
| Ottoman Empire, Founding of | c. 1299 | Anatolia (modern Turkey) | State formation |
| Ottoman Interregnum | 1402–1413 | Ottoman Empire | Civil war / Interregnum |
| Overthrow of the Kingdom of Hawaii | 1893 | Hawaii | Coup d’état |
Descriptions
Oath of the Tennis Court
A pivotal moment in the French Revolution where members of the Third Estate swore not to separate until a new constitution was written, signaling a shift in power from the monarchy.
Occupation of Alcatraz
A 19-month long protest where Native American activists occupied Alcatraz Island, bringing international attention to the plight of Indigenous peoples in the United States and sparking the Red Power movement.
Occupation of Japan
The period following World War II when Allied forces, primarily the United States, occupied Japan, leading to widespread political, economic, and social reforms, including a new democratic constitution.
Occupation of the Ruhr
An occupation of Germany’s industrial heartland by French and Belgian troops after Germany defaulted on its war reparation payments, leading to hyperinflation and international tension.
October Crisis
A series of events in Canada involving the kidnapping of two government officials by the Front de libération du Québec (FLQ), which led to the only peacetime invocation of the War Measures Act.
October Manifesto
A document issued by Tsar Nicholas II in response to the 1905 Revolution, promising civil liberties and an elected parliament (the Duma), though its power was ultimately limited.
October Revolution
The Bolshevik-led insurrection that overthrew the provisional government in Petrograd, establishing the world’s first socialist state and profoundly shaping 20th-century history.
October War (Yom Kippur War)
A major conflict initiated by a coalition of Arab states led by Egypt and Syria against Israel. The war’s impact on oil prices led to a global energy crisis.
O. K. Corral, Gunfight at the
A legendary 30-second shootout between lawmen and outlaws in the American West. The event has been famously depicted in numerous books and films, becoming a symbol of the Old West.
Oklahoma City bombing
A domestic terrorist truck bombing of a federal building that killed 168 people. Until the September 11 attacks, it was the deadliest act of terrorism in U.S. history.
Oldcastle’s Rebellion
An unsuccessful Lollard uprising led by Sir John Oldcastle against King Henry V. It aimed to reform the Church in England but resulted in a crackdown on the Lollard heresy.
Olympic Games, Ancient, Founding of
The traditional date for the start of the ancient Olympic Games, a series of athletic competitions among city-states that became a cornerstone of ancient Greek culture and religious practice.
Olympic Games, Modern, Revival of
The first international Olympic Games held in modern history, reviving the ancient Greek tradition. This event established the multi-sport competition that continues to this day.
Onin War
A destructive civil war that devastated Kyoto and marked the end of the Ashikaga shogunate’s effective power, ushering in the violent, century-long Sengoku (“Warring States”) period.
Opening of Japan
The forced end of Japan’s 220-year policy of national seclusion. U.S. Commodore Matthew Perry’s expedition compelled Japan to open its ports to international trade, triggering rapid modernization.
Operation Barbarossa
The codename for Nazi Germany’s massive invasion of the Soviet Union during World War II. It was the largest land invasion in history and opened the brutal Eastern Front.
Operation Desert Storm
The combat phase of the Gulf War, in which a U.S.-led coalition expelled Iraqi forces from Kuwait. It was notable for its televised coverage and use of modern military technology.
Operation Eagle Claw
A failed U.S. military operation to rescue 52 American hostages held in Tehran. The mission’s failure was a major blow to American prestige and the Carter administration.
Operation Enduring Freedom
The official name for the War in Afghanistan, launched by the U.S. and its allies in response to the September 11 attacks to dismantle al-Qaeda and remove the Taliban from power.
Operation Iraqi Freedom
The U.S.-led invasion of Iraq that toppled the government of Saddam Hussein. The conflict was justified by claims of WMDs but led to a long and difficult insurgency.
Operation Market Garden
A bold but ultimately failed Allied military operation during WWII. It aimed to secure key bridges in the Netherlands to allow a rapid advance into Germany but met with heavy resistance.
Operation Mincemeat
A successful British deception operation during WWII. It used a corpse with false papers to mislead the Germans about the Allied invasion of Sicily, saving thousands of lives.
Operation Overlord
The codename for the Battle of Normandy, the successful Allied invasion of German-occupied Western Europe. The D-Day landings on June 6 marked the beginning of the end for Nazi Germany.
Operation Paperclip
A secret U.S. intelligence program that brought over 1,600 German scientists, engineers, and technicians to the U.S. after WWII, fueling the Cold War space and arms race.
Operation Rolling Thunder
A sustained aerial bombing campaign conducted by the U.S. against North Vietnam during the Vietnam War. It was intended to pressure North Vietnam but ultimately failed to achieve its strategic goals.
Operation Sea Lion
Nazi Germany’s ambitious but ultimately aborted plan to invade the United Kingdom during WWII. The plan was postponed indefinitely after the Luftwaffe failed to gain air superiority in the Battle of Britain.
Operation Torch
The successful Anglo-American invasion of French North Africa during World War II. It was the first time U.S. and British armies worked together on an invasion and helped clear the Axis from North Africa.
Opium War, First
A conflict between Britain and Qing dynasty China over the British opium trade. China’s defeat led to the Treaty of Nanking, which ceded Hong Kong to Britain and began a period of unequal treaties.
Opium War, Second
A war pitting the British and French Empires against Qing China. It further weakened the dynasty, legalized the opium trade, and opened more of China to foreign influence.
Oprichnina
A period of mass repression, public executions, and land confiscation in Russia instituted by Tsar Ivan the Terrible. He used his black-clad police force, the Oprichniki, to crush opposition.
Orange Revolution
A series of massive, non-violent protests and civil disobedience in Ukraine following a fraudulent presidential election. The protests led to the annulment of the result and a new, fairer election.
Oregon Trail, Opening of the
The beginning of large-scale wagon train migration along the 2,170-mile route from Missouri to Oregon. This mass movement was central to the westward expansion of the United States.
Orgreave, Battle of
One of the most violent confrontations in UK industrial history, where thousands of striking miners clashed with police. It was a pivotal and symbolic moment in the 1984–85 miners’ strike.
Orléans, Siege of
A turning point in the Hundred Years’ War where the French, inspired by Joan of Arc, successfully repelled an English siege. This victory boosted French morale and paved the way for Charles VII’s coronation.
Orphan Train Movement
A supervised welfare program that transported an estimated 200,000 orphaned or homeless children from crowded Eastern cities to foster homes in the rural Midwest, forever changing their lives.
Ostend Manifesto
A controversial document written by American diplomats arguing that the U.S. should purchase Cuba from Spain, and if refused, declare war. It inflamed sectional tensions over slavery in the U.S.
Ottoman Empire, Founding of
The traditional date for the establishment of the Ottoman state by Osman I in northwestern Anatolia. It grew from a small principality into one of the world’s most powerful and long-lasting empires.
Ottoman Interregnum
An 11-year period of civil war among the sons of Sultan Bayezid I after his defeat by Timur. The conflict temporarily halted Ottoman expansion and threatened to destroy the young empire.
Overthrow of the Kingdom of Hawaii
The illegal overthrow of Queen Liliʻuokalani and the Hawaiian monarchy by a group of American and European businessmen, with support from U.S. Marines, leading to U.S. annexation.