|Centuries:||18th century – 19th century – 20th century|
|Decades:||1810s 1820s 1830s – 1840s – 1850s 1860s 1870s|
|Years:||1840 1841 1842 – 1843 – 1844 1845 1846|
- February 6 – The Virginia Minstrels perform the first minstrel show (Bowery Amphitheatre, New York City).
- February 8 – Earthquakes in Guadeloupe magnitude 8.5, 5000 people report killed.
- February 11 – Giuseppe Verdi's opera I Lombardi premieres in Milan.
- May 18 – The Disruption of the Church of Scotland took place in Edinburgh.
- May 22 – The first major wagon train headed for the northwest sets out with one thousand pioneers from Elm Grove, Missouri, on the Oregon Trail.
- July 19 – The SS Great Britain is launched from Bristol.
- August 15 – Tivoli Gardens, one of the oldest still intact amusement parks in the world, opened in Copenhagen, Denmark.
- October 13 – In New York City, Henry Jones and 11 others found B'nai B'rith (the oldest Jewish service organization in the world).
- November 28 – Ka La Ku'oko'a: Hawaiian Independence Day. The Kingdom of Hawai`i was officially recognized by the United Kingdom and France as an independent nation.
- The world's first commercial Christmas cards are printed by Sir Henry Cole in London.
- December 17 – First publication of Charles Dickens' A Christmas Carol.
- James Joule quantifies the conversion of work into heat.
- In Barbados, the first black man, Samuel Jackson Prescod, is elected to the House of Assembly.
- The Danish government re-establishes the althing in Iceland as an advisory body.
- The first tunnel under the Thames is finished.
- Argentina supports Rosas of Uruguay and begins a siege of Montevideo.
- Quaternions are discovered by William Rowan Hamilton.
- The Economist is first published.
- Bishop's University is founded.
- Abbeville is founded by descendants of Acadians from Nova Scotia.
- for more information, see Category:1843 births.
- for more information, see Category:1843 deaths.