Famous birthdays, deaths and events of 1812
- January 8 - Sigismond Thalberg, French pianist and composer (d. 1871)
- January 13 - Victor de Laprade, French poet and critic (d. 1883)
- January 15 - Peter Christen Asbjørnsen, Norwegian writer (d. 1885)
- February 7 - Charles Dickens, English novelist (d. 1870)
- February 15 - Charles Lewis Tiffany, American jeweler (d. 1902)
- February 28 - Berthold Auerbach, German poet and author (d. 1882)
- March 6 - Aaron Lufkin Dennison American watch manufacturer, (d. 1895)
- March 22 - Stephen Pearl Andrews, American abolitionist (d. 1886)
- April 2 - Louise-Marie of France, queen of Belgium (d. 1850)
- April 6 - Alexander Herzen, Russian writer (d. 1870)
- April 22 - Solomon Caesar Malan, British orientalist (d. 1894)
- April 27 - Friedrich von Flotow, German composer (d. 1883)
- April 30 - Kaspar Hauser, German mystery boy (d. 1833)
- May 7 - Robert Browning, English poet (d. 1889)
- May 12 - Edward Lear, British author and poet (d. 1888)
- June 18 - Ivan Goncharov, Russian author (d. 1891)
- July 15 - James Hope-Scott, English barrister (d. 1873)
- November 14 - Aleardo Aleardi, Italian poet (d. 1878)
- November 14 - Maria Christina of Savoy, queen of the Two Sicilies (d. 1836)
- November 11 - Platon Levshin, Metropoitan of Moscow (b. 1737)
- December 27 - Joanna Southcott, an English self-described religious prophetess.
- January 19 - Peninsular War: After a ten day siege, Arthur Wellesley, 1st Duke of Wellington, orders British soldiers of the Light and third divisions to storm Ciudad Rodrigo.
- February 2 - Russia establishes a fur trading colony at Fort Ross, California.
- February 7 - The strongest in a series of earthquakes strikes New Madrid, Missouri.
- February 11 - Massachusetts governor Elbridge Gerry gerrymanders for the first time.
- February 27 - Poet Lord Byron gives his first address as a member of the House of Lords, in defense of Luddite violence against Industrialism in his home county of Nottinghamshire.
- March 16 - Battle of Badajoz (March 16
- March 26 - An earthquake destroys Caracas, Venezuela.
- April 4 - U.S. President James Madison enacted a ninety-day embargo on trade with the United Kingdom.
- April 30 - The Territory of Orleans becomes the 18th U.S. state under the name Louisiana.
- May 11 - Prime Minister Spencer Perceval is assassinated by John Bellingham in the lobby of the House of Commons, London.
- May 27 - South American Wars of Independence: In Bolivia, the Battle of La Coronilla, in which the women from Cochabamba fight against the Spanish army.
- June 1 - War of 1812: U.S. President James Madison asks the Congress to declare war on the United Kingdom.
- June 4 - Following Louisiana's admittance as a U.S. state, the Louisiana Territory is renamed the Missouri Territory.
- June 18 - War of 1812: The U.S. Congress declares war on the United Kingdom of Great Britain and Ireland.
- June 22 - Napoleon declares war on Russia and invades.
- June 23 - War of 1812: Great Britain revokes the restrictions on American commerce, thus eliminating one of the chief reasons for going to war.
- June 24 - Napoleonic Wars: Napoleon's Grande Armée crosses the Neman River beginning his invasion of Russia.
- July 12 - War of 1812: The United States invades Canada at Windsor, Ontario.
- July 22 - Napoleonic Wars: Peninsular War
- August 5 - War of 1812: Tecumseh's Native American force ambushes Thomas Van Horne's 200 Americans at Brownstone Creek, causing them to flee and retreat.
- August 16 - War of 1812: American General William Hull surrenders Fort Detroit without a fight to the British Army.
- August 19 - War of 1812: American frigate USS Constitution defeats the British frigate HMS Guerrière off the coast of Nova Scotia, Canada earning her nickname "Old Ironsides".
- September 7 - Napoleonic Wars: Battle of Borodino
- September 14 - Napoleonic Wars: French grenadiers enter Moscow. The Fire of Moscow begins as soon as Russian troops leave the city.
- September 15 - The French army under Napoleon reaches the Kremlin in Moscow.
- September 16 - Russians set fire to Moscow shortly after midnight
- September 18 - The 1812 Fire of Moscow dies down after destroying more than three quarters of the city. Napoleon returns from the Petrovsky Palace to the Moscow Kremlin, spared from the fire.
- October 9 - War of 1812: In a naval engagement on Lake Erie, American forces capture two British ships: HMS Detroit and HMS Caledonia.
- October 13 - War of 1812: Battle of Queenston Heights
- October 14 - Work on London's Regent's Canal starts.
- October 19 - Napoleon I of France retreats from Moscow.
- October 24 - Napoleonic Wars: The Battle of Maloyaroslavets takes place near Moscow.
- November 3 - Napoleon's armies are defeated at Vyazma
- November 17 - Napoleonic Wars: Battle of Krasnoi.
- December 12 - French invasion of Russia comes to an end.
- December 29 - The USS Constitution under the command of Captain William Bainbridge, captures the HMS Java off the coast of Brazil after a three hour battle.