Year 1781 (MDCCLXXXI) was a common year starting on Monday (link will display the full calendar) of the Gregorian calendar (or a common year starting on Friday of the 11-day slower Julian calendar).

Events of 1781

January - June

• January - William Pitt the Younger, later Prime Minister, enters Parliament.
• January 2 - Virginia passes a law ceding its western land claims, paving the way for Maryland to ratify the Articles of Confederation.
• January 5 - American Revolution: Richmond, Virginia is burned by British naval forces led by Benedict Arnold.
• January 6 - Battle of Jersey: The British beat the French in what is technically the last battle fought in the British Islands (coming after the Battle of Culloden in 1745). It is the last attempt by France to invade Jersey militarily.
• January 17 - American Revolution - Battle of Cowpens: Americans under Daniel Morgan defeat British forces.
• February 2 - The Articles of Confederation are ratified by Maryland, the 13th and final state to do so.
• March - Riots break out in Socorro and spread to other towns.
• March 1 - The United States Continental Congress implements the Articles of Confederation, forming its Perpetual Union as the United States in Congress Assembled.
• March 13 - Sir William Herschel discovers the planet Uranus. Originally he calls it Georgium Sidus (George's Star) in honour of King George III of England.
• March 15 - American Revolution - Battle of Guilford Court House: American General Nathanael Greene loses to the British.

March 13: Uranus discovered [image in false color].

• May 18 - An army sent from Lima put down the rebellions and captures and savagely execute Túpac Amaru II.
• June 4 - The commission agrees to the rebel's terms: reduction of the alcabala and of the Indians' forced tribute, abolition of the new taxes on tobacco and prederence for Creoles over peninsulares in government positions.

July - December

• July 27 - French spy Francis Henry de la Motte is executed in Tyburn Prison in England for high treason.
• July 29 - American Revolution - Skirmish at the House in the Horseshoe: A Tory force under David Fanning attacks Phillip Alston's smaller force of Whigs at Alston's home in Cumberland County, North Carolina (in present day Moore County, North Carolina). Alston's troops surrender after Fanning's men attempt to ram the house with a cart of burning straw.
• August 30 - American Revolution: A French fleet under Comte de Grasse enters Chesapeake Bay, cutting British General Charles Cornwallis off from escape by sea.
• September 4 - Los Angeles is founded as El Pueblo de Nuestra Señora La Reina de Los Ángeles de Porciuncula (City of Our Lady the Queen of the Angels of Porciuncula) by a group of 44 Spanish settlers.
• September 5 - American Revolution: A British fleet under Thomas Graves arrives and fights de Grasse, but to no effect.
• September 6 - American Revolution - Battle of Groton Heights: The British army attacks a fort in Groton, Connecticut.
• September 10 - American Revolution: Graves gives up trying to break through the now-reinforced French fleet and returns to New York, leaving Cornwallis to his fate.
• October 19 - American Revolution: Following the Siege of Yorktown, General Charles Cornwallis surrenders to General George Washington at Yorktown, Virginia, ending the armed struggle of the American Revolution.
• October 20 - A Patent of Tolerance, providing limited freedom of worship, is approved in the Habsburg Monarchy.
• November 5 - John Hanson is elected President of the Continental Congress.
• November 29
  • The slave ship Zong dumps its living cargo into the sea in order to claim insurance.
  • Henry Hurle officially founds the Ancient Order of Druids(AOD) in London, England.
• December 12 - Second Battle of Ushant: A British fleets defeats French ships.

Undated

• Bank of North America is chartered by the Continental Congress.
• Charles Messier publishes the final catalog of Messier objects.
• Carl Wilhelm Scheele discovers tungsten.
• Immanuel Kant publishes his Critique of Pure Reason.
• Jeremy Bentham formulates utilitarian ethics.
• Reverend Samuel Peters publishes his General History of Connecticut, using the term blue law for the first time.
• Founding of:
  • Phillips Exeter Academy
  • Washington Academy (later Washington and Jefferson College)
• Joseph II, Holy Roman Emperor abolishes serfdom.

Births

• January 26 - Achim von Arnim, German writer (d. 1831)
• January 30 - Adelbert von Chamisso, German writer (d. 1838)
• February 17 - Rene Theophile Hyacinthe Laennec, French physician and inventor (d. 1826)
• March 4 - Rebecca Gratz, American educator and philanthropist (d. 1869)
• March 13 - Karl Friedrich Schinkel, German architect and painter (d. 1841)
• April 2 - Bhagwan Swaminarayan, Hindu spiritual leader and believed by a few to be god (d. 1830)
• June 9- George Stephenson, English engineer (d. 1848)
• June 21 - Siméon-Denis Poisson, French mathematician and physicist (d. 1840)
• July 6
  • Thomas Stamford Raffles, English founder of Singapore (d. 1826)
  • John D. Sloat, American naval officer (d. 1867)
• July 27 - Mauro Giuliani, Italian composer (d. 1829)
• September 3 - Eugène de Beauharnais, French nobleman, son of Napoleon's wife Josephine (d. 1824)
• September 6 - Anton Diabelli, Austrian music publisher, editor, and composer (d. 1858)
• October 1 - James Lawrence, U.S. Navy officer (d. 1813)
• November 6 - Lucy Aikin, English writer (d. 1864)
• November 20 - Karl Friedrich Eichhorn, German jurist (d. 1854)
• November 29 - Andrés Bello, Venezuelan poet, lawmaker, teacher, philosopher and sociologist (d. 1865)
• November 30 - Alexander Berry, Scottish adventurer and Australian pioneer (d. 1873)
• December 11 - Sir David Brewster, Scottish physicist (d. 1868)
• date unknown
  • William Williams of Wern, minister (d. 1840)
  • Shaka Zulu, King of the Zulu people (d. 1828)

Deaths

• January 12 - Richard Challoner, English Catholic prelate (b. 1691)
• January 15 - Marianne Victoria of Borbón, queen regent of Portugal (b. 1718)
• February 15 - Gotthold Ephraim Lessing, German author and philosopher (b. 1729)
• February 23 - George Taylor, American signer of the Declaration of Independence
• February 24 - Edward Capell, English critic (b. 1713)
• March 18 - Anne Robert Jacques Turgot, Baron de Laune, French statesman and economist (b. 1727)
• April 23 - James Abercrombie, British general (b. 1706)
• April 28 - Cornelius Harnett, American delegate to the Continental Congress (b. 1723)
• May 8 - Richard Jago, English poet (b. 1715)
• May 18 - Túpac Amaru II, rebel (b. 1742)
• May 27 - Giovanni Battista Beccaria, Italian physicist (b. 1716)
• July 18 - Padre Francisco Garcés, Spanish missionary (killed) (b. 1738)
• July 23 - John Joachim Zubly, Swiss-born Continental Congressman (b. 1724)
• September 28 - William Henry Nassau de Zuylestein, 4th Earl of Rochford, British diplomat and statesman (b. 1717)
• October 16 - Edward Hawke, 1st Baron Hawke, British naval officer (b. 1705)
• November 4 - Johann Nikolaus Götz, German poet (b. 1721)
• date unknown - Peter Scheemakers, Flemish sculptor (b. 1691)