Events of 1846

• January 5 – The United States House of Representatives votes to stop sharing the Oregon Territory with the United Kingdom.

• February 10 – Many Mormons begin their migration west from Nauvoo, Illinois to the Great Salt Lake, led by Brigham Young.

• February 18 – Beginning of the Galician peasant revolt.

• February 19 – In Austin, Texas, the newly formed Texas state government is officially installed.

• February 26 – The Liberty bell is cracked while being rung for George Washington's birthday.

• March 10 – Prince Osahito, fourth son of deceased Emperor Ninko of Japan, becomes Emperor Kōmei.

• April 25 – Mexican-American War: Open conflict begins over border disputes of Texas' boundaries.

• May 8 – Mexican-American War – Battle of Palo Alto: Zachary Taylor defeats a Mexican force north of the Rio Grande at Palo Alto, Texas in the first major battle of the war.

• May 13 – Mexican-American War: The United States declares war on Mexico.

• May 16 – Under the leadership of British Prime Minister Robert Peel, the British Parliament repeals the Corn Laws, replacing the old Colonial mercantile trade system with Free Trade.

• 16 May– revolutionary insurrection in Portugal (would be crushed by royalist troops on 22 February on the next year)

• May 17 – The Saxophone is patented by Adolphe Sax.

• May 25 – The Royal Geographical Society awards Paweł Edmund Strzelecki a Gold Medal "for exploration in the south eastern portion of Australia".

• June 10 – Mexican-American War: The California Republic declares independence from Mexico.

• June 14 – Bear Flag Revolt: American settlers in Sonoma, California start a rebellion against Mexico and proclaim the California Republic.

• June 15

• *The Oregon Treaty establishes the 49th parallel as the border between the United States and Canada, from the Rocky Mountains to the Strait of Juan de Fuca.

• *Launceston Church Grammar School opens for the first time.

• June 16 – Pope Pius IX succeeds Pope Gregory XVI as the 255th pope.

• July 7 – Acting on instructions from Washington, DC, Commodore John Drake Sloat orders his troops to occupy Monterey and Yerba Buena thus beginning the United States annexation of California.

• September – The Second Carlist War, or the War of the Matiners or Madrugadores begins in Spain.

• September 19 – The Virgin Mary is said to have appeared to two children in La Salette, France.

• September 23 – Discovery of Neptune: The planet is observed for the first time by German astronomers Johann Gottfried Galle and Heinrich Louis d'Arrest as predicted by the British astronomer John Couch Adams and the French astronomer Urbain Le Verrier, although the planet did not get its current name for many years.

• October 1 – Christ College, Tasmania opens with the hope that it would develop along the lines of an Oxbridge college and provide the basis for university education in Tasmania. Today, it is the oldest tertiary instituition in Australia.

• December 28: Iowa is admitted as the 29th U.S. state.

Undated

• The portion of the District of Columbia that was ceded by Virginia in 1790 is re-ceded to Virginia.

• Electric Telegraph Company founded in Britain.

• Elias Howe patents the sewing machine.

• Rotary printing press invented, making rapid printing of newspapers possible.

• Cholera epidemic in England.

Ongoing events

• Mexican-American War (1846–1848)

• Great Irish Famine (1845–1849)

Births

• January 5 – Rudolf Christoph Eucken, German writer, Nobel Prize laureate (d. 1926)

• January 27 – M. Lewis Clark American founder of Kentucky Derby (d. 1899)

• February 2 – Francis Marion Smith, American borax magnate (d. 1931)

• February 9 – Wilhelm Maybach, German automobile designer (d. 1929)

• February 18 – Wilson Barrett, English actor (d. 1904)

• February 26 – William F. "Buffalo Bill" Cody, American frontiersman (d. 1917)

• April 4 – Comte de Lautreamont, French writer (d. 1870)

• May 5 – Henryk Sienkiewicz, Polish author, Nobel Prize laureate (d. 1916)

• June 11 – William Louis Marshall, American general and engineer (d. 1920)

• June 27 – Charles Stewart Parnell, Irish political leader (d. 1891)

• July 17 – Tokugawa Iemochi, the 14th shogun of the Tokugawa Shogunate of Japanese (d. 1866)

• July 26 – Texas Jack Omohundro, American frontier scout, actor, and cowboy (d. 1880)

• August 23 – Alexander Milne Calder, American sculptor (d. 1923)

• September 16 – Anna Kingsford, British spiritual writer, doctor, feminist and pioneering vegetarian.

• November 25 – Carrie Nation, American temperance advocate (d. 1911)

Deaths

• February 21 – Emperor Ninko of Japan (b. 1800)

• March 17 – Friedrich Bessel, German mathematician and astronomer (b. 1784)

• May 23 – Franciszek Ksawery Drucki-Lubecki, Polish politician (b. 1778)

• June 1 – Pope Gregory XVI (b. 1765)

• June 8 – Rodolphe Töpffer, Swiss author, painter, and caricature artist (b. 1799)

• August 16 – Sylvain Charles Valée, Marshal of France (b. 1773)

• September 14 – Jacques Dupre, Louisiana State Representative, State Senator, and Governor (b.1773)

• September 23 – John Ainsworth Horrocks, English-born explorer of South Australia (b. 1818)

• September 26 – Thomas Clarkson, English Abolitionist (b. 1760)

• November 6

• *Karol Marcinkowski, Polish physician and social activist (b. 1800)

• *Alexander Chavchavadze, Georgian Romantic poet and military figure (b. 1786)

• 18 December – Emilie Högquist, Swedish dramatic star (d. 1812)