| 21 January 1276 | Papal States, Italy [administration] | Peter of Tarantaise is elected Pope Innocent V. |
| 21 January 1337 | France [births and deaths] | Charles V the Wise, King of France 1364–80 who led France to recovery after the first phase of the Hundred Years' War (1337–1453), born in Vincennes, France (–1380). |
| 21 January 1793 | France [births and deaths] | Louis XVI, King of France 1774–92, now known as ‘Citizen Capet’, is guillotined in Paris, France (38). |
| 21 January 1824 | USA [births and deaths] | Thomas ‘Stonewall’ Jackson, one of the ablest Confederate generals in the American Civil War, born in Clarksburg, Virginia (–1863). |
| 21 January 1846 | UK [newspapers] | The Daily News is founded in London, England, with the author Charles Dickens as editor. It is the first cheap daily newspaper in Britain. |
| 21 January 1924 | [births and deaths] | Vladimir Ilyich Lenin, founder of the Russian Communist Party, leader of the Russian Revolution, and head of the Soviet Union 1917–24, dies in Gorky, near Moscow, USSR (53). |
| 21 January 1924 | USSR [political events] | A struggle for the leadership of the USSR begins following the death of the Soviet leader Vladimir Ilyich Lenin. |
| 21 January 1939 | Germany [administration] | The German Führer dismisses Hjalmar Schacht as president of the Reichsbank for opposing his rearmament expenditure. He replaces him with Walther Funk, minister of economics. |
| 21 January 1950 | England [births and deaths] | George Orwell, English novelist who wrote Animal Farm and Nineteen Eighty-Four, dies in London, England (46). |
| 21 January 1954 | USA [technology] | The first nuclear-powered submarine, the Nautilus, is launched by the USA at Groton, Connecticut. It is also the largest submarine, at 97 m/319 ft long. |
| 21 January 1959 | USA [births and deaths] | Cecil B DeMille, US film director and producer known for his spectacular films such as The Greatest Show on Earth, dies in Hollywood, California (77). |
| 21 January–8 April 1968 | North Vietnam, South Vietnam [Vietnam War (1954–75)] | 5,000 US marines and South Vietnamese soldiers are besieged by two North Vietnamese army divisions at Khe Sanh in the north of South Vietnam, in one of the fiercest battles of the entire Vietnam War. |
| 21 January 1973 | USA [social legislation] | In the case Roe v. Wade, the US Supreme Court rules that state restrictions on abortion are unconstitutional and that a woman has the right to an abortion within the first six months of pregnancy. This provokes militant anti-abortion protests. |
| 21 January 1976 | UK, France [aircraft] | The British-French supersonic airliner Concorde begins a regular passenger service across the Atlantic; it is the world's first scheduled supersonic passenger service. |
| 21 January 1976 | UK, Bahrain, France, Brazil [aircraft] | Two Concorde aircraft make their first commercial flights, from London, England, to Bahrain and from Paris, France, to Rio de Janeiro, Brazil. |
| 21 January 1998 | Cuba [Catholicism] | Pope John Paul II visits Cuba for the first time, where he criticizes the repression of personal and religious freedoms under the communist government of President Fidel Castro. |
