| 21 March 1084 | Papal States, Holy Roman Empire [wars] | King Henry IV of Germany captures Rome and besieges Pope Gregory VII in the Castel Sant' Angelo. |
| 21 March 1173 | England, France [revolution] | The ‘young’ king Henry and his brothers Richard, Geoffrey, and John rebel against their father, King Henry II of England, with the help and encouragement of King Louis VII of France. |
| 21 March 1282 | England [wars] | David ap Gruffydd, brother of Llywelyn ap Gruffydd, Prince of Wales, begins a widespread Welsh revolt against King Edward I of England by capturing Hawarden Castle. A Welsh ‘parliament’ soon commits the Welsh to war. |
| 21 March 1685 | Germany [births and deaths] | Johann Sebastian Bach, leading German composer of the baroque period, born in Eisenach, Thuringia, Germany (–1750). |
| 21 March 1788 | USA [natural disasters] | A great fire in New Orleans, Louisiana, destroys nearly the entire city. |
| 21 March 1801 | France, Spain, Portugal, UK, North America [treaties] | The Treaty of Aranjuez is signed between France and Spain, formalizing their ultimatum to Portugal to break its traditional allegiance to Britain. Spain also agrees to cede the North American territory of Louisiana to France. |
| 21 March 1804 | France [legislation] | The Civil Code (renamed the Code Napoleon in 1807) is promulgated in France, providing a uniform civil law (previously French law was split between Roman law in the south and custom law in the north). |
| 21 March 1878 | USA [births and deaths] | Jack Johnson, US boxer and the first black person to win the world heavyweight boxing championship (1908–15), born in Galveston, Texas (–1946). |
| 21 March–5 April 1918 | France, Germany [World War I (1914–18)] | The German army launches a spring offensive on the Western Front with the Second Battle of the Somme, and advances 64 km/40 mi towards Paris, France. |
| 21 March 1919 | Hungary [law and government] | A soviet government is formed in Budapest, Hungary, under the revolutionary leader Béla Kun. |
| 21 March 1960 | South Africa [political events] | The ‘Sharpeville massacre’ occurs in a township near Vereeniging (south of Johannesburg), South Africa, where members of the Pan-African Congress demonstrating against pass laws are fired on by police, killing 69 demonstrators and wounding 186 more. |
| 21 March 1961 | UK [popular music] | The British rock group the Beatles make their British debut at the Cavern Club in Liverpool, England. |
