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1789 (MDCCLXXXIX) was a common year starting on Thursday of the Gregorian calendar and a common year starting on Monday of the Julian calendar, the 1789th year of the Common Era (CE) and Anno Domini (AD) designations, the 789th year of the 2nd millennium, the 89th year of the 18th century, and the 10th and last year of the 1780s decade. As of the start of 1789, the Gregorian calendar was 11 days ahead of the Julian calendar, which remained in localized use until 1923.
- January – Emmanuel Joseph Sieyès publishes the pamphlet What Is the Third Estate? (Qu'est-ce que le tiers-état?), influential on the French Revolution.
- January 7 – The United States presidential election, 1788–89 and House of Representatives elections are held.
- January 9 – Treaty of Fort Harmar: The terms of the Treaty of Fort Stanwix (1784) and the Treaty of Fort McIntosh, between the United States Government and certain native American tribes, are reaffirmed, with some minor changes.
- January 21 – The first American novel, The Power of Sympathy or the Triumph of Nature Founded in Truth, is printed in Boston, Massachusetts. The anonymous author is William Hill Brown.
- January 23 – Georgetown University is founded in Georgetown, Maryland (today part of Washington, D.C.), as the first Roman Catholic college in the United States.
- April 1 – At Federal Hall, the United States House of Representatives attains its first quorum, and elects congressman Frederick Muhlenberg as the first Speaker of the House.
- April 6 – At Federal Hall, the United States Senate attains its first quorum, and elects John Langdon of Pennsylvania as its first President pro tempore. Later that day, the Senate and the House of Representatives meet in joint session for the first time, and the electoral votes of the first U.S. Presidential election are counted. General George Washington is certified as President-elect, and John Adams is certified as Vice-President elect.
- April 7 – Selim III (1789–1807) succeeds Abdul Hamid I (1773–1789), as Ottoman Sultan.
- April 21 – John Adams takes office as the first Vice President of the United States, and begins presiding over the United States Senate.
- April 28 – Mutiny on the Bounty: Fletcher Christian leads the mutiny on the British Royal Navy ship HMS Bounty against Captain William Bligh, in the Pacific Ocean.
- April 30 – George Washington is inaugurated at Federal Hall in New York City, beginning his term as the first President of the United States.
- May 5 – In France, the Estates-General convenes for the first time in 175 years.
- June – The Inconfidência Mineira is the first attempt at Brazilian independence from Portugal.
- July – An estimated 150,000 of Paris's 600,000 people are without work.
- July 1 – The comic ballet La fille mal gardée, choreographed by Jean Dauberval, is first presented under the title Le ballet de la paille, at the Grand Théâtre de Bordeaux, at Bordeaux, France.
- July 4 – The U.S. Congress passes its first bill, setting out tariffs. 
- July 9
- July – Storofsen flood in Norway.
- July 10 – Alexander Mackenzie reaches the Mackenzie River Delta.
- July 11 – Louis XVI of France dismisses popular Chief Minister Jacques Necker.
- July 12 – An angry Parisian crowd, inflamed by a speech from journalist Camille Desmoulins, demonstrates against the King's decision to dismiss Minister Necker.
- July 13 – The people begin to seize arms for the defense of Paris.
- July 14 – The French Revolution (1789–1799) begins with the Storming of the Bastille: Citizens of Paris storm the fortress of the Bastille, and free the only seven prisoners held. In rural areas, peasants attack manors of the nobility.
- July 14 – Survivors of the mutiny on the Bounty, including Captain William Bligh and 18 others, reach Timor after a nearly 4,000-mile (6,400 km) journey in an open boat.
- July 27 – The first agency of the Federal government of the United States under the new Constitution, the Department of Foreign Affairs  (from September 15 renamed the Department of State), is established.
- August 4 – In France, members of the Constituent Assembly take an oath to end feudalism, and abandon their privileges.
- August 7 – The United States Department of War is established.
- August 18 – The Liège Revolution breaks out in the Prince-Bishopric of Liège.
- August 21 – A proposal for a Bill of Rights is adopted by the United States House of Representatives.
- August 26 – The Declaration of the Rights of Man and of the Citizen is proclaimed in France, by the Constituent Assembly.
- August 28 – William Herschel discovers Enceladus, one of Saturn's moons.
- September 2 – The United States Department of the Treasury is founded. 
- September 11 - Alexander Hamilton is appointed as the first United States Secretary of the Treasury.
- September 22 –
- September 24 – The Judiciary Act of 1789 establishes the federal judiciary, and the United States Marshals Service.
- September 25 – The United States Congress proposes a set of 12 amendments to the U.S. constitution, for ratification by the states.  Ratification for 10 of these proposals is completed on December 5, 1791, creating the United States Bill of Rights.
- September 26 — Thomas Jefferson, U.S. Minister to France, is appointed as the first U.S. Secretary of State. 
- September 29 – The U.S. Department of War establishes the nation's first regular army, with a strength of several hundred men.
- Joseph II, Holy Roman Emperor, decrees that all peasant labor obligations be converted into cash payments.
- The Traité Élémentaire de Chimie (Elementary Treatise of Chemistry), an influential chemistry textbook by Antoine Lavoisier, is published; translated into English in 1790, it comes to be considered the first modern chemical textbook.
- German chemist Martin Heinrich Klaproth discovers the element uranium, while studying the mineral pitchblende.
- The Bengal Presidency first establishes a penal colony, in the Andaman Islands.
- Thomas Jefferson returns from Europe, bringing the first macaroni machine to the United States.
- Influenced by Dr. Benjamin Rush's argument against the excessive use of alcohol, about 200 farmers in a Connecticut community form a temperance movement in the United States.
- Fort Washington (Cincinnati, Ohio) is built to protect early U.S. settlements in the Northwest Territory.
- Former slave Olaudah Equiano's autobiography The Interesting Narrative of the Life of Olaudah Equiano, one of the earliest published works by a black writer, is published in London.
- March 16 – Georg Ohm, German physicist (d. 1854)
- April 15 – Diego Noboa, 4th President of Ecuador (d. 1870)
- April 22 – Manuel Gómez Pedraza, 6th President of Mexico (d. 1851)
- May 1 – George Fife Angas, founder of South Australia (d. 1879)
- May 24 – Cathinka Buchwieser, German operatic singer and actress
- June 8 – Queen Sunwon, Korean regent (d. 1857)
- June 30 – Horace Vernet, French painter (d. 1863)
- July 19 – John Martin, English painter (d. 1854)
- August 6 – Friedrich List, German journalist (d. 1846)
- August 21 – Augustin-Louis Cauchy, French mathematician (d. 1857)
- August 28 – Stéphanie de Beauharnais, Grand Duchess of Baden (d. 1860)
- September 4 – Charles Gaudichaud-Beaupré, French botanist (d. 1854)
- September 15 – James Fenimore Cooper, American writer (d. 1851)
- September 28 – Richard Bright (physician), English physician; Father of Nephrology (d. 1858)
- October 8 – William John Swainson, English naturalist, artist (d. 1855)
- November 5 – William Bland, Australian politician (d. 1868)
- December 15
- December 22 – Levi Woodbury, American politician, Associate Justice of the Supreme Court of the United States (d. 1851)
- December 25 – Elizabeth Jesser Reid, English social reformer, founder of Bedford College (d. 1866)
- December 28 – Catharine Sedgwick, American writer (d. 1867)
- date unknown – Mohammad Ibrahim Zauq, Urdu poet (d. 1854)
- January 1 – Fletcher Norton, 1st Baron Grantley, English politician (b. 1716)
- January 4 – Thomas Nelson Jr., American signer of the Declaration of Independence and Governor of Virginia (1781) (b. 1738)
- January 8 – Jack Broughton, English boxer (b. 1703)
- January 10 – James Mitchell Varnum, American brigadier general of the Revolutionary War, Continental Congressman for Rhode Island (b. 1748)
- January 13 – Joseph Spencer, American major general of the Revolutionary War, Continental Congressman for Connecticut (b. 1714)
- January 23 – Frances Brooke, English writer (b. 1724)
- January 25 – James Randolph Reid, American Continental Congressman for Connecticut (b. 1750)
- February 12 – Ethan Allen, American major general of the Revolutionary War, Vermont statesman (b. 1738)
- February 19 – Nicholas Van Dyke, American lawyer and President of Delaware (b. 1738)
- April 7
- April 13 – Joseph Spencer, American colonel of the Revolutionary War, Continental Congressman for New Hampshire (b. 1739)
- April 26 – Count Petr Ivanovich Panin, Russian soldier (b. 1721)
- May 9 – Jean-Baptiste Vaquette de Gribeauval, French artillery specialist (b. 1715)
- May 25 – Anders Dahl, Swedish botanist (b. 1751)
- June 4 – Louis Joseph, Dauphin of France, son of Louis XVI of France (tuberculosis) (b. 1781)
- July 13 – Victor de Riqueti, marquis de Mirabeau, French economist (b. 1715)
- July 14 – Jacques de Flesselles, French provost (assassinated) (b. 1721)
- July 15 – Jacques Duphly, French composer (b. 1715)
- July 22 – Joseph Foullon de Doué, French politician (executed) (b. 1715)
- July 30 – Giovanna Bonanno, Italian poisoner, alleged witch (b. c. 1713)
- September 4 – Paul Spooner, American lieutenant governor of Vermont (1782–1787) (b. 1746)
- September 23
- October 27 – John Cook, American farmer, President of Delaware (b. 1730)
- November 10 – Richard Caswell, American major general of the Revolutionary War, Continental Congressman and Governor of North Carolina (1776–80, 1785–87) (b. 1729)
- November 17 – Samuel Holden Parsons, American major general of the Revolutionary War, member of the Connecticut House of Representatives (b. 1737)
- December 3 – Claude Joseph Vernet, French painter (b. 1714)
- December 10 – William Pierce, American member of the Georgia House of Representatives, Continental Congressman for Georgia (c. 1753)
- December 12 – John Ponsonby, Irish politician (b. 1713)
- December 23 – Charles-Michel de l'Épée, French philanthropist, developer of signed French (b. 1712)
- date unknown – Mary Evans, Welsh religious leader (b. 1735)
- ^ "219 years ago - Description of a Slave Ship". Rare Book Collections @ Princeton. Princeton University Library. 2008. Archived from the original on February 4, 2014. Retrieved 2013-03-19.
- ^ "The Brookes - visualising the transatlantic slave trade". 1807 Commemorated. University of York Institute for the Public Understanding of the Past. 2007. Retrieved 2013-03-19.
- ^ a b c d e f g Harper's Encyclopaedia of United States History from 458 A. D. to 1909, ed. by Benson John Lossing and, Woodrow Wilson (Harper & Brothers, 1910) p168-169
- ^ "The establishment of the Department of War". clerk.house.gov. Archived from the original on March 7, 2011.
- ^ Adamson, Barry (2008). Freedom of Religion, the First Amendment, and the Supreme Court: How the Court Flunked History. Pelican Publishing. p. 93.
- ^ Journal of the House of Representatives of the United States, 1789-1793, August 21, 1789, p. 85
- ^ "The First Supreme Court". History.com. Archived from the original on May 1, 2009. Retrieved 2008-09-24.
- ^ "BBC History British History Timeline". Archived from the original on 2007-09-09. Retrieved 2007-09-03.