1837 1838 1839 - 1840 - 1841 1842 1843
| Decades: |
1810s 1820s 1830s - 1840s - 1850s 1860s 1870s
| Centuries: |
18th century - 19th century - 20th century
1840 is a leap year starting on Wednesday (link will take you to calendar).
- January 3 - One of the predecessor papers to the Herald Sun of Melbourne, Australia, The Port Phillip Herald, is founded by George Cavanaugh.
- January 10 - Uniform penny postage introduced in the UK.
- January 19 - Captain Charles Wilkes circumnavigates Antarctica, claiming what became known as Wilkes Land for the United States.
- January 20 - Dumont D'Urville discovers [[Ad�lie Land]], Antarctica.
- January 22 - British colonists reach New Zealand. Official founding date of Wellington.
- February 6 - Treaty of Waitangi, document granting British sovereignty in New Zealand, is signed.
- February 10 - Queen Victoria of the United Kingdom marries Prince Albert of Saxe Coburg-Gotha.
- February 11 - Gaetano Donizetti's opera La Fille du Regiment premieres in Paris.
- March 1 - William Hobson, first Governor of New Zealand, suffers a stroke.
- March 1 - Adolphe Thiers becomes prime minister of France.
- May 1 - Britain issues the Penny Black, world's first postage stamp.
- May 6 - The Penny Black, world's first postage stamp becomes valid for the pre-payment of postage.
- May 7 - The Great Natchez Tornado: A massive tornado strikes Natchez, Mississippi during the early afternoon hours. Before it was over, 317 people had lost their lives and 209 were injured. It is the second deadliest tornado in U.S. history.
- July 4 - The Cunard Line's 700-ton wooden paddlewheel steamer RMS Britannia departs from Liverpool bound for Halifax, Nova Scotia on the first transatlantic passenger cruise.
- July 15 – Austria, Britain, Prussia, and Russia sign a London Treaty with the Sublime Porte, ruler of the Ottoman Empire.
- September 10 - Ottoman and British troops bombard Beirut and land troops on the coast to pressure Egyptian Muhammad Ali to retreat from the country.
- October 7 - Willem II becomes King of the Netherlands.
- October 14 – Maronite leader Bashir II surrenders to the British forces and goes into exile in Malta.
- November - William Henry Harrison defeats Martin Van Buren in the U.S. presidential election.
- David Livingstone leaves for Africa.
- Punch caricature magazine begins publication.
- Pedro II is declared "of age" prematurely and begins to reassert central control in Brazil.
- Mount Allison University is founded in Sackville, New Brunswick, Canada.
- January 3 - Father Damien, missionary priest in Hawai'i (d. 1888)
- February 4 - Hiram Stevens Maxim, inventor of Maxim Gun (d. 1916)
- February 5 - John Boyd Dunlop, inventor (d. 1921)
- February 11 - Samuel Dana Greene, Lieutenant Commander (Union Navy)
- February 21 - Murad V, future Ottoman sultan (d. 1904)
- February 22 - August Bebel, politician (d. 1913)
- February 23 - Carl Menger, economist (d. 1921)
- February 29 - John Philip Holland, developer of the first submarine (d. 1914)
- March 28 - Emin Pasha, German doctor, naturalist to Africa (d. 1892)
- April 2 - Emile Zola, writer (d. 1902)
- April 22 - Odilon Redon, painter (d. 1916)
- April 27 - Edward Whymper, explorer - first ascent of the Matterhorn (1865) (d. 1911)
- May 7 - Pyotr Ilyich Tchaikovsky, composer (d. 1893)
- June 2 - Thomas Hardy, novelist (d. 1928)
- August 4 - Richard von Krafft-Ebing, sexologist
- November 12 - Auguste Rodin, sculptor
- November 14 - Claude Monet, painter
- November 21 - Victoria, Princess Royal, "Vicky," eldest daughter of Queen Victoria and Prince Albert
- November 29 - Rhoda Broughton (d. 1920)
- January 6 - Fanny Burney, novelist
- January 10 - Princess Elizabeth of the United Kingdom, Dowager Landgravine of Hesse-Homburg, aunt of Queen Victoria
- January 22 - Johann Friedrich Blumenbach, German anthropologist
- April 25 - Sim�on-Denis Poisson, mathematician, geometer, physicist (b. 1781)
- May 27 - Niccolo Paganini, violinist and composer
- June 7 - King Frederick William III of Prussia
- Emperor Kokaku of Japanaf:1840
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