1842

January–March

• January
  • Michael Alexander takes office, as the first appointee to the Anglican-German Bishopric in Jerusalem.
  • American medical student William E. Clarke of Berkshire Medical College becomes the first person to administer an inhaled anesthetic, to facilitate a surgical procedure (dental extraction).
• January 6–13 – First Anglo-Afghan War – Massacre of Elphinstone's army (Battle of Gandamak): British East India Company troops are destroyed by Afghan forces on the road from Kabul to Jalalabad, Afghanistan, by Akbar Khan, son of Dost Mohammad Khan.
• January 8 – Delft University of Technology is established by William II of the Netherlands, as a 'Royal Academy for the education of civilian engineers'.
• January 23 – Antarctic explorer James Clark Ross, charting the eastern side of James Ross Island, reaches a Farthest South of 78°09'30"S.
• February 1 – Willamette University is established in Salem, Oregon.
• February 7 – Battle of Debre Tabor: Ras Ali Alula, Regent of the Emperor of Ethiopia, defeats warlord Wube Haile Maryam of Semien.
• March – Commonwealth v. Hunt: The Massachusetts Supreme Court makes strikes and unions legal in the United States.
• March 2 – Gaylad, ridden by Tom Olliver, wins the Grand National at Aintree Racecourse in England.
• March 5 – Mexican troops led by Ráfael Vásquez invade Texas, briefly occupy San Antonio, and then head back to the Rio Grande. This is the first such invasion since the Texas Revolution.
• March 9 – Giuseppe Verdi's third opera Nabucco premieres at La Scala in Milan; its success establishes Verdi as one of Italy's foremost operatic composers.
• March 17 – The Female Relief Society of Nauvoo, forerunner to the philanthropic and educational women's organization of the Church of Jesus Christ of Latter-day Saints (LDS Church) is formally organized.
• March 28 – The Vienna Philharmonic Orchestra, founded by Otto Nicolai, performs its first concert.
• March 30 – American physician and pharmacist Crawford Long administers an inhaled anesthetic (diethyl ether) to facilitate a surgical procedure (removal of a neck tumor).
• March 31 – The Middleton Junction and Oldham Branch Railway line is opened up to Werneth in North West England.

April–June

• April 13 – First Anglo-Afghan War – Battle of Jellalabad: British troops are victorious.
• May 5–8 – Great fire of Hamburg in Germany destroys around one-third of the city centre and kills 51.
• May 8 – Versailles rail accident: A train traveling between Versailles and Paris, France derails, due to a broken locomotive axle, and catches fire, killing at least 55 passengers in the locked carriages.
• May 11 – The Income Tax Act establishes the first peacetime income tax in the United Kingdom; 7 pence in the pound, for incomes over 150 pounds.
• May 19 – Dorr Rebellion: Militiamen supporting Thomas Wilson Dorr attack the arsenal in Providence, Rhode Island, but are repulsed.
• June 4 – In South Africa, hunter Dick King rides into a British military base in Grahamstown, to warn that the Boers have besieged Durban (he had left 11 days earlier). The British army dispatches a relief force.
• June 13 – Queen Victoria becomes the first reigning British monarch to travel by train, on the Great Western Railway between Slough and London Paddington station.
• June 18 – A primary school system is established in Sweden.
• June – James Nasmyth patents the steam hammer in the United Kingdom.

July–September

• July 8 – A total solar eclipse occurs in Asia.
• July 13 – The Tri-Kap fraternity is founded at Dartmouth College (the oldest local fraternity in the United States).
• August 4 – The Armed Occupation Act is signed, providing for the armed occupation and settlement of the unsettled part, of the Peninsula of East Florida.
• August 9 – The Webster–Ashburton Treaty is signed, establishing the United States–Canada border east of the Rocky Mountains.
• August 10 – The Mines Act 1842 becomes law, prohibiting underground work for all women and boys under 10 years old in the United Kingdom.
• August 14 – American Indian Wars: United States general William J. Worth declares the Second Seminole War to be over.
• August 29 – The Treaty of Nanking, an unequal treaty between Britain and Qing dynasty China, ends the First Opium War, and establishes Hong Kong as a British colony until 1997.
• September – Wesleyan University is established in Ohio.
• September 16–17 – The Treaty of Chushul ends the Sino-Sikh War.

October–December

• October 5 – Josef Groll brews the first pilsner beer in the city of Pilsen, Bohemia (now the Czech Republic).
• October 29 – The Iberian Peninsula is struck by a category 2 hurricane.
• November 10 & 19 – London debtor's prisons the Fleet Prison and Marshalsea are closed and inmates transferred to Queen's Bench Prison. Pentonville Prison for criminals is completed in north London this year.
• November 26 – The University of Notre Dame in Notre Dame, Indiana (United States) is established by Father Edward Sorin, of the Roman Catholic Congregation of Holy Cross.
• December 7 – The New York Philharmonic, founded by Ureli Corelli Hill, performs its first concert.
• December 20 – The Citadel, The Military College of South Carolina, is established.

Date unknown

• The Polynesian islands of Tahiti and Tahuata are declared a protectorate of France.
• The New Zealand seat of government moves from Russell to Auckland.
• Dzogchen Monastery, in Sichuan, China, is almost completely destroyed by an earthquake.
• English palaeontologist Richard Owen coins the name Dinosauria, hence the Anglicized dinosaur.
• Julius von Mayer proposes that work and heat are equivalent.
• Pickelhaube helmet introduced in the Prussian Army.
• The Sons of Temperance is founded in New York City.
• Beecham's Pills (a laxative) is first marketed in Lancashire, England, by Thomas Beecham, forming the basis of the Beecham Group and GSK plc pharmaceutical companies.
• Founding of:
  • Cumberland University (in Lebanon, Tennessee).
  • Hollins University (in Roanoke, Virginia by Charles Cocke).
  • Villanova University (in Villanova, Pennsylvania by the Augustinian order).
  • Indiana University Maurer School of Law at Indiana University Bloomington.
  • Delft University of Technology (in Delft, Netherlands).

January–June

• January 11 – William James, American psychologist, philosopher (d. 1910)
• January 15 – Mary MacKillop, first Australian saint (d. 1909)
• February 3 – Sidney Lanier, American writer (d. 1881)
• February 7 – Alexandre Ribot, 46th Prime Minister of France (d. 1923)
• February 11
  • Erik Gustaf Boström, 2-Time Prime Minister of Sweden (d. 1907)
  • Maria Louise Eve, American author (d. 1900)
• February 23 – Karl Robert Eduard von Hartmann, German philosopher (d. 1906)
• February 24 – Arrigo Boito, Italian poet, composer (d. 1918)
• February 25 – Karl May, German writer (d. 1912)
• March 2 – Carl Jacobsen, Danish brewer, patron of the arts after whom the Carlsberg brewery was named (d. 1914)
• March 5 – A. Viola Neblett, American activist, suffragist, women's rights pioneer (d. 1897)
• March 10 – Mykola Lysenko, Ukrainian composer (d. 1912)
• March 18 – Stéphane Mallarmé, French poet (d. 1898)
• March 25 – Susan Augusta Pike Sanders, American teacher, clubwoman, author; national president of the Woman's Relief Corps (d. 1931)
• March 26 – Alexandre Saint-Yves d'Alveydre, French occultist (d. 1909)
• March 30 – John Fiske, American philosopher (d. 1901)
• April 2 – Dominic Savio, Italian adolescent student of John Bosco (d. 1857)
• April 17 – Maurice Rouvier, Prime Minister of France (d. 1911)
• May 4 – Marietta Bones, American suffragist, social reformer, philanthropist (d. 1901)
• May 7 – Isala Van Diest, Belgian physician (d. 1916)
• May 8 – Emil Christian Hansen, Danish fermentation physiologist (d. 1909)
• May 13 – Sir Arthur Sullivan, English composer (d. 1900)
• June 11 – Carl von Linde, German scientist, engineer (d. 1934)
• June 12 – Rikard Nordraak, Norwegian composer (d. 1866)
• June 16 – David Herold, accomplice of John Wilkes Booth (d. 1865)
• June 24 – Ambrose Bierce, American writer, satirist (d. ca. 1914)
• June 25 – Eloy Alfaro, 15th President of Ecuador (d. 1912)

July–December

• July 2 – Albert Ladenburg, German chemist (d. 1911)
• July 4 – Hermann Cohen, German-Jewish philosopher (d. 1918)
• July 14 – Christian Lundeberg, 10th Prime Minister of Sweden (d. 1911)
• July 18 – William D. Coleman, 13th President of Liberia (d. 1908)
• July 19 – Lydia Hoyt Farmer, American author, women's rights activist (d. 1903)
• July 30 – Thomas J. O'Brien, American politician, diplomat (d. 1933)
• August 21 – Harriet Earhart Monroe, American lecturer, educator, writer, producer (d. 1927)
• August 23 – Osborne Reynolds, Irish engineer, physicist (d. 1912)
• September 3 – John Devoy, Irish rebel leader, exile (d. 1928)
• September 10 – Henry Granger Piffard (d. 1910), New York dermatologist and author of the first systematic treatise on dermatology in America
• September 13 – John H. Bankhead, American senator (d. 1920)
• September 20 – Sir James Dewar, Scottish chemist, physicist (d. 1923)
• September 22 – Abdul Hamid II, Ottoman Sultan (d. 1918)
• September 29 – Sir Joseph Palmer Abbott, Australian politician and solicitor (d. 1901)
• October 3 – Frederick Rodgers, American admiral (d. 1917)
• October 14 – Joe Start, American baseball player (d. 1927)
• October 17 – Gustaf Retzius, Swedish physician, anatomist (d. 1919)
• October 27 – Giovanni Giolitti, 5-time prime minister of Italy (d. 1928)
• October 28 – Anna Elizabeth Dickinson, American orator (d. 1932), younger sister of journalist Susan E. Dickinson
• November 12
  • Ōyama Iwao, Japanese field marshal, a founder of the Imperial Japanese Army (d. 1916)
  • John Strutt, 3rd Baron Rayleigh, English physicist, Nobel Prize laureate (d. 1919)
• November 26 – Madeleine Brès, French physician (d. 1921)
• December 2 – C. W. Alcock, English footballer, football official (d. 1907)
• December 3 – Ellen Swallow Richards, American chemist (d. 1911)
• December 9 – Peter Kropotkin, Russian anarchist (d. 1921)
• December 12 – Alfred Parland, Russian architect (d. 1919)

January–June

• January 12 – Johanna Stegen, German heroine (b. 1793)
• January 19 – Comte Siméon Joseph Jérôme, French jurist and politician (b. 1749)
• February 15 – Carlo Andrea Pozzo di Borgo, Corsican politician, Russian diplomat (b. 1764)
• March 4 – James Forten, African American abolitionist
• March 6 – Constanze Mozart, German-born wife of Wolfgang Amadeus Mozart (b.1762)
• March 13
  • Samuel Eells, American founder of Alpha Delta Phi fraternity (b. 1810)
  • Henry Shrapnel, English army officer, inventor (b. 1761)
• March 15 – Luigi Cherubini, Italian composer (b. 1760)
• March 23 – Stendhal, French novelist (b. 1783)
• March 30 – Louise Élisabeth Vigée Le Brun, French painter (b. 1755)
• May 8 – Jules Dumont d'Urville, French explorer (b. 1790)
• May 12 – Walenty Wańkowicz, Polish painter (b. 1799)
• June 9 – Maria Dalle Donne, Bolognese physician (b. 1778)
• June 18 – François-André Baudin, French admiral (b. 1774)

July–December

• July 13 – Prince Ferdinand Philippe, Duke of Orléans, French prince (b. 1810)
• July 21 – Laura M. Hawley Thurston, American poet and educator (b. 1812)
• July 25 – Dominique Jean Larrey, French surgeon (b. 1766)
• July 28 – Clemens Brentano, German poet (b. 1778)
• August 24 – Leona Vicario, leader of Mexican War of Independence and wife of Andrés Quintana Roo (b. 1789)
• September 10
  • William Hobson, Irish-born officer in the British Royal Navy, first Governor-General of New Zealand and co-author of Treaty of Waitangi (b. 1792)
  • Letitia Christian Tyler, First Lady of the United States 1841–1842 (b. 1790)
• September 15 – Francisco Morazán, Honduran-born politician, President of Federal Republic of Central America (b. 1792)
• October 2 – William Ellery Channing, American Unitarian theologian, minister (b. 1780)
• October 20 – Grace Darling, English heroine (b. 1815)
• October 24 – Bernardo O'Higgins, first Chilean head of state after independence (b.1778)
• October 25 – Sampson Salter Blowers, American lawyer, jurist (b. 1742)
• December 1 – Philip Spencer, American founder of Chi Psi fraternity, midshipman aboard the USS Somers, hanged for mutiny.
• December 12 – Robert Haldane, British theologian (b. 1764)
• December 24 – Adam Gillies, Lord Gillies, Scottish judge (b. 1760)

Date unknown

• Nodira, Uzbek poet, stateswoman (b. 1792)