Year 1840 (MDCCCXL) was a leap year starting on Wednesday (link will display the full calendar) of the Gregorian calendar (or a leap year starting on Monday of the 12-day slower Julian calendar).

Events of 1840

January - June

January 13: Steamship Lexington sinks.

• January 3 - One of the predecessor papers of the Herald Sun of Melbourne, Australia, The Port Phillip Herald, is founded.
• January 10 - Uniform penny postage is introduced in the UK.
• January 13 - The steamship Lexington burns and sinks in icy waters, 4 miles off the coast of Long Island; 139 die, only 4 survive.
• January 19 - Captain Charles Wilkes circumnavigates Antarctica, claiming what becomes known as Wilkes Land for the United States.
• January 20
  • Dumont D'Urville discovers Adélie Land, Antarctica.
  • The first public school is established in Rockingham County.
• January 22 - British colonists reach New Zealand, officially founding Wellington.
• February - Rhodes blood libel against the Jews of Rhodes.
• February 5 - The murder of a Capuchin friar and his Greek servant leads to the Damascus affair, a highly publicized case of blood libel against the Jews of Damascus.
• February 6 - The Treaty of Waitangi, 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, the first Governor of New Zealand, suffers a stroke.
  • Adolphe Thiers becomes prime minister of France.
• April 15 - King's College Hospital opens in Portugal Street, London.
• May 1 - Britain issues the Penny Black, the world's first postage stamp.
• May 6 - The Penny Black, the 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 iss over, 317 people are killed and 109 injured. It is the second deadliest tornado in U.S. history.
• May 21 - New Zealand is declared a British colony.

July - December

July 4: RMS Britannia.

• 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 the London Treaty with the Sublime Porte, ruler of the Ottoman Empire.
• July 23 - The Province of Canada is created by the Act of Union.
• August 10 - Fortsas hoax: A number of book collectors gather in Binche, Belgium to attend a non-existent book auction of the late "Count of Fortsas".
• September 10 - Ottoman and British troops bombard Beirut and land troops on the coast to pressure Egyptian Muhammad Ali to retreat from the country.
• September 16 - Joseph Strutt hands over the deeds and papers concerning the Arboretum, which later becomes England's first public park.
• September 30 - The frigate Belle-Poule arrives in Cherbourg, bringing back the remains of Napoléon from Saint Helena to France. He is buried in the Invalides.
• October 7 - Willem II becomes King of the Netherlands.
• November 7 - U.S. presidential election, 1840: William Henry Harrison defeats Martin Van Buren.
• December 7 - David Livingstone leaves Britain for Africa.
• December 7 - The Stockport Viaduct (located in Greater Manchester, England) is completed. It is the largest brick structure in Western Europe.

Undated

The frigate Belle-Poule brings back the remains of Napoléon to France.

• Louis Agassiz publishes 2-volume work entitled Etudes sur les glaciers ("Study on Glaciers"), the first major work to scientifically propose that the Earth has been subject to a past ice age.
• 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.
• The Washingtonian Temperance Society is founded.
• The first English translation of Goethe's Theory of Colours by Charles Eastlake is published.
• Frederick William IV starts to rule in Prussia.

Ongoing events

• First Opium War (1839-1842)

Births

January - June

• January 3 - Father Damien, Belgian missionary priest (d. 1889)
• January 22 - Ernest Roland Wilberforce, English bishop (d. 1907)
• January 23 - Ernst Abbe, German physicist (d. 1905)
• January 26 - John Clayton Adams, British landscape artist (d. 1906)
• February 4 - Hiram Stevens Maxim, American firearms inventor (d. 1916)
• February 5 - John Boyd Dunlop, Scottish inventor (d. 1921)
• February 21 - Murad V, Ottoman Sultan (d. 1904)
• February 22 - August Bebel, German politician (d. 1913)
• February 23 - Carl Menger, Austrian economist (d. 1921)
• February 29 - John Philip Holland, Irish inventor (d. 1914)
• March 28 - Emin Pasha, German doctor and African administrator (d. 1892)
• April 2 - Emile Zola, French writer (d. 1902)
• April 22 - Odilon Redon, French painter (d. 1916)
• April 27 - Edward Whymper, English mountaineer (d. 1911)
• May 7 - Pyotr Ilyich Tchaikovsky, Russian composer (d. 1893)
• May 13 - Alphonse Daudet, French writer (d. 1897)
• June 2 - Thomas Hardy, English writer (d. 1928)
• June 10 - Theodor Philipsen Danish painter (d. 1920)

July - December

• August 4 - Richard von Krafft-Ebing, German sexologist (d. 1902)
• October 9 - Simeon Solomon, British artist (d. 1905)
• October 16 - Kuroda Kiyotaka, Prime Minister of Japan (d. 1900)
• November 12 - Auguste Rodin, French sculptor (d. 1917)
• November 14 - Claude Monet, French painter (d. 1926)
• November 21 - Victoria, Princess Royal of the United Kingdom and Empress of Germany (d. 1901)
• November 29 - Rhoda Broughton, Welsh writer (d. 1920)

Deaths

January - June

• January 6 - Fanny Burney, English novelist (b. 1752)
• January 22 - Johann Friedrich Blumenbach, German anthropologist (b. 1752)
• February 13 - Nicolas Joseph Maison, French marshal and Minister of War (b. 1770)
• April 25 - Siméon-Denis Poisson, French mathematician, geometer, and physicist (b. 1781)
• May 1 - Joseph Williamson, philanthropist and builder of Williamson's tunnels (b. 1769)
• May 6 - Demetrius Augustine Gallitzin, Russian aristocrat and priest (b. 1770)
• May 7 - Caspar David Friedrich, German artist (b. 1774)
• May 11 - Thomas Cooper, American political philosopher (b. 1759)
• May 26 - Sidney Smith, British admiral (b. 1764)
• May 27 - Nicolò Paganini, Italian violinist and composer (b. 1782)
• June 7 - King Frederick William III of Prussia (b. 1770)

July - December

• July 7 - Nikolai Stankevich, philosopher and poet (b. 1813)
• August 25 - Karl Leberecht Immermann, novelist and dramatist (b. 1796)
• September 11 - Jean-Gabriel Perboyre, Catholic missionary and martyr in China
• September 14 - Joseph Smith, Sr., father of Joseph Smith, Jr.
• September 18 - Constantine Samuel Rafinesque, polymath (b. 1783)
• September 20 - José Gaspar Rodríguez de Francia, the first leader of independent Paraguay (b. 1766)
• November 2 - Józef Kossakowski (colonel), Polish-Lithuanian statesman (b. 1771)

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