The 1780s decade ran from January 1, 1780, to December 31, 1789.
March 13, 1781: Uranus
- October 2 – American Revolutionary War – In Tappan, New York, British spy John André is hanged by American forces.
- October 7 – American Revolutionary War – Battle of Kings Mountain: Patriot militia forces annihilate Loyalists under British Major Patrick Ferguson, at Kings Mountain, South Carolina.
- October 10–16 – The Great Hurricane flattens the islands of Barbados, Martinique and Sint Eustatius; 22,000 are killed.
- November 4 – Rebellion of Túpac Amaru II: In the Spanish Viceroyalty of Peru, Túpac Amaru II leads an uprising of Aymara and Quechua peoples and mestizo peasants as a protest against the Bourbon Reforms.
- November 28 – A lightning strike in Saint Petersburg begins a fire that burns 11,000 homes.
- November 29 – Maria Theresa of Austria dies, and her Habsburg dominions pass to her ambitious son, Joseph II, who has already been Holy Roman Emperor since 1765.
- November 30 – American Revolutionary War: The British San Juan Expedition is forced to withdraw.
- December 16 – Emperor Kōkaku accedes to the throne of Japan.
- December 20 – The Fourth Anglo-Dutch War begins.
- Jose Gabriel Kunturkanki, businessman and landowner, proclaims himself Inca Túpac Amaru II.
- The Duke of Richmond calls, in the House of Lords of Great Britain, for manhood suffrage and annual parliaments, which are rejected.
- Jeremy Bentham's Introduction to Principles of Morals and Legislation, presenting his formulation of utilitarian ethics, is printed (but not published) in London.
- Nikephoros Theotokis starts introducing Edinoverie, an attempt to integrate the Old Believers into Russia's established church.
- The Woodford Reserve bourbon whiskey distillery begins operation in Kentucky.
- In Ireland, Lady Berry, who is sentenced to death for the murder of her son, is released when she agrees to become an executioner (she retires in 1810).
- The original Craven Cottage is built by William Craven, 6th Baron Craven, in London, on what will become the centre circle of Fulham F.C.'s pitch.
- The amateur dramatic group Det Dramatiske Selskab is founded in Christiania, Norway.
- Western countries pay 16,000,000 ounces of silver for Chinese goods.
- The Kingdom of Great Britain reaches c.9 million population.
- January – William Pitt the Younger, later Prime Minister of Great Britain, enters Parliament, aged 21.
- January 1 – Industrial Revolution: The Iron Bridge opens across the River Severn in England.
- 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 Revolutionary War: Richmond, Virginia is burned by British naval forces, led by Benedict Arnold.
- January 6 – Battle of Jersey: British troops prevent the French from occupying Jersey in the Channel Islands.
- January 17 – American Revolutionary War – Battle of Cowpens: The American Continental Army, under Daniel Morgan, decisively defeats British forces in South Carolina.
- February 2 – The Articles of Confederation are ratified by Maryland, the 13th and final state to do so.
- February 3 – Fourth Anglo-Dutch War – Capture of Sint Eustatius: British forces take the Dutch Caribbean island of Sint Eustatius, with only a few shots fired. On November 26 it is retaken by Dutch-allied French forces.
- March – Riots break out in Socorro, Santander, 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 Great Britain.
- March 15 – American Revolutionary War – Battle of Guilford Court House: American General Nathanael Greene loses to the British.
- April 6 – The rebellion by Túpac Amaru II, against the Spanish colonial government of Peru, is ended as Tupac, his wife and two of his sons are captured at Checacupe. 
- April 10 – Future U.S. President Andrew Jackson, age 14, is slashed by a British officer's sword at his home near Waxhaw, North Carolina, after refusing to clean the officer's boots, an event that leaves physical and psychological scars. 
- April 14 – The Continental Congress votes a resolution thanking U.S. Captain John Paul Jones for his services. 
- April 18 – Future New York mayor James Duane, North Carolina representative William Sharpe and future Connecticut governor Oliver Wolcott deliver the first report to the U.S. Continental Congress about the national debt and report it to be 24,057,157 and 2/5 dollars. 
- April 25 – The Battle of Hobkirk's Hill took place in Camden, South Carolina
- May 9 – General John Campbell, defender of the British colony of West Florida, surrenders the capital at Pensacola to Spanish forces commanded by Bernardo de Galvez. 
- May 18 – A Spanish army sent from Lima puts down the Inca rebellions, and captures and savagely executes Túpac Amaru II.
- June 4 – The commission agrees to the rebels' terms: reduction of the alcabala and of the Indians' forced tribute, abolition of the new taxes on tobacco, and preference for Criollos over peninsulares in government positions.
- October 12 – The first bagpipes competition is held in the Masonic Arms, Falkirk, Scotland.
- 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 Toleration, providing limited freedom of worship, is approved in the Habsburg Monarchy.
- November 5 – John Hanson is elected President of the Continental Congress.
- November 29
- December – A school is founded in Washington County, Pennsylvania that will later be known as Washington & Jefferson College.
- December 12 – American Revolutionary War – Second Battle of Ushant: The British Royal Navy, commanded by Rear Admiral Richard Kempenfelt in HMS Victory, decisively defeats the French fleet in the Bay of Biscay.
- January 7 – The first American commercial bank (Bank of North America) opens.
- January 15 – Superintendent of Finance Robert Morris goes before the U.S. Congress, to recommend establishment of a national mint and decimal coinage.
- January 23 – The Laird of Johnstone (George Ludovic Houston) invites people to buy marked plots of land which, when built upon, form the planned town of Johnstone, Scotland, to provide employment for his thread and cotton mills.
- February 5 – The Spanish defeat British forces, and capture Menorca.
- February 27 – The British House of Commons votes against further war in America, paving the way for the Second Rockingham ministry and the Peace of Paris.
- March 8 – Gnadenhutten massacre: In Ohio, 29 Native American men, 27 women, and 34 children are killed by white militiamen, in retaliation for raids carried out by another Native American group.
- March 14 – Battle of Wuchale: Emperor Tekle Giyorgis pacifies a group of Oromo near Wuchale.
- March 27 – Charles Watson-Wentworth, 2nd Marquess of Rockingham becomes Prime Minister of the United Kingdom.
- March 31 (Easter Sunday) – Mission San Buenaventura is founded in Las Californias, part of the Viceroyalty of New Spain.
- April 12 – Battle of the Saintes: A British fleet under Admiral Sir George Rodney defeats a French fleet under the Comte de Grasse, in the West Indies.
- April 19 – John Adams secures recognition of the United States as an independent government by the Dutch Republic. During this visit, he also negotiates a loan of five million guilders, financed by Nicolaas van Staphorst and Wilhelm Willink.
- April 21 – A Lak Mueang (city pillar) is erected on Rattanakosin Island, located on the eastern bank of the Chao Phraya River, by order of King Rama I, an act considered the founding of the capital city of Bangkok.
- May 17 – The Parliament of Great Britain passes the Repeal of Act for Securing Dependence of Ireland Act, a major component of the reforms collectively known as the Constitution of 1782, which restore legislative independence to the Parliament of Ireland.
- June 18 – In Switzerland, Anna Göldi is sentenced to death for witchcraft (the last legal witchcraft sentence).
- June 20 – The bald eagle is chosen as the emblem of the United States of America. On the same day, the Confederation Congress adopts the design for the Great Seal of the United States.
- July – Joseph II, Holy Roman Emperor, receives a visit from Pope Pius VI.
- July 1 – Raid on Lunenburg: American privateers attack the British settlement at Lunenburg, Nova Scotia.
- July 16–August 29 – The Masonic Congress of Wilhelmsbad, Germany, one of history's most important ever secret society congresses, takes place. High-degree Freemasons from the whole of Europe spend the time deliberating the fate of the rite of Strict Observance, and hierarchy of the governing bodies of world Freemasonry, at the Hanau-Wilhelmsbad spa.
- July 16 – Wolfgang Amadeus Mozart's opera Die Entführung aus dem Serail premieres at the Burgtheater in Vienna.
- August 7
- August 21 – A fire breaks out in Constantinople at 9:00 in the evening and burns for two and a half days, destroying thousands of buildings and one-half of the city, and killing hundreds of people.
- September 7 – Correspondents to the Jewish Calendar, 5543.
- September 17 – 1782 Central Atlantic hurricane devastates a British Royal Navy fleet off the Grand Banks of Newfoundland with the loss of 3,500 lives.
- Chief Kamehameha I of Hawaii gains control of the northern part of the island of Hawaii, after defeating his cousin Kīwalaʻō.
- Princess Yekaterina Vorontsova-Dashkova is the first woman in the world to direct a scientific academy, the Imperial Academy of Arts and Sciences.
- London creates the Foot Patrol for public security.
- The British Parliament extends James Watt's patent for the steam engine to the year 1800.
- The North Carolina General Assembly incorporates Washington, North Carolina.
- In China, the Siku Quanshu is completed, the largest literary compilation in China's history (surpassing the Yongle Encyclopedia of the 15th century). The books are bound in 36,381 volumes (册) with more than 79,000 chapters (卷), comprising about 2.3 million pages, and approximately 800 million Chinese characters.
- Foundation of the first theater in the Baltic, the Riga City Theater.
- Saint Petersburg, Russia has 300,000 inhabitants.
- January 20 – At Versailles, Great Britain signs preliminary peace treaties with the Kingdom of France and the Kingdom of Spain.
- January 23 – The Confederation Congress ratifies two October 8, 1782, treaties signed by the United States with the United Netherlands.
- February 3 – American Revolutionary War: Great Britain acknowledges the independence of the United States of America. At this time, the Spanish government does not grant diplomatic recognition.
- February 4 – American Revolutionary War: Great Britain formally declares that it will cease hostilities with the United States.
- February 5 – 1783 Calabrian earthquakes: The first of a sequence of five earthquakes strikes Calabria, Italy (February 5–7, March 1 & 28), leaving 50,000 dead.
- February 7 – Great Siege of Gibraltar abandoned.
- February 26 – The United States Continental Army's Corps of Engineers is disbanded.
- March 5 – The last celebration of Massacre Day is held in Boston, Massachusetts.
- March 15 – Newburgh Conspiracy: A potential uprising in the Continental Army stationed at Newburgh, New York is defused, when George Washington asks the officers to support the supremacy of the United States Congress.
- April – Peace and Commercial Treaty signed between the newly-formed United States and Sweden in Paris, among the first acts of state concluded between the U.S. and a foreign power.
- April 8 – The Crimean Khanate, which has existed since 1441 and is a late remnant of the Mongol Golden Horde, is annexed by the Russian Empire of Catherine the Great.
- April 15 – Preliminary articles of peace ending the American Revolutionary War are ratified by the Congress of the Confederation in the United States.
- April 18 – Three-Fifths Compromise: the first instance of black slaves in the United States of America being counted as three fifths of persons (for the purpose of taxation), in a resolution of the Congress of the Confederation. (This was later adopted in the 1787 Constitution.)
- May 13 – The Society of the Cincinnati, a fraternal organization for American veterans of the American Revolution, is formed in Newburgh, New York.
- May 18 – The first United Empire Loyalists, fleeing the new United States, reach Parrtown in Saint John, New Brunswick, Canada.
- May 26 – A Great Jubilee Day, celebrating the end of the American Revolution, is held in Trumbull, Connecticut.
- June 4 or June 5 – The Montgolfier brothers publicly demonstrate their montgolfière hot air balloon at Annonay, France.
- June 8 – The volcano Laki in Iceland begins an 8-month eruption, starting the chain of natural disasters known as the Móðuharðindin, killing tens of thousands throughout Europe, including up to 33% of Iceland's population, and causing widespread famine. It has been described as one of "the greatest environmental catastrophes in European history".
- General George Washington sends a letter to the 13 governors of the confederation of United States regarding the needs of the nation.
- July 16 – Grants of land in Canada to American Loyalists are announced.
- July 24 – The Treaty of Georgievsk is signed between Imperial Russia and the Kingdom of Kartli-Kakheti, making Georgia a protectorate of Russia.
- August 4 – Mount Asama, the most active volcano in Japan, begins a climactic eruption, killing roughly 1,400 people directly and exacerbating a famine, resulting in another 20,000 deaths (Edo period, Tenmei 3).
- August 10 – The British East India Company packet ship Antelope (1781) is wrecked off Ulong Island in the Palau (Pelew) group, resulting in the first sustained European contact with those islands.
- August 18 – The 1783 Great Meteor passes on a 1,000-mile track across the North Sea, Great Britain and France, prompting scientific discussion.
- August 27 – Jacques Charles and Les Frères Robert launch the world's first hydrogen-filled balloon, Le Globe, in Paris.
- September 3 – Peace of Paris: A treaty between the United States and Great Britain is signed in Paris, formally ending the American Revolutionary War, in which Britain recognized the independence of the United States; and treaties are signed between Britain, France, and Spain at Versailles, ending hostilities with the Franco-Spanish Alliance. This is also the beginning of the Old West.
- September 9 – Dickinson College is chartered in Carlisle, Pennsylvania.
- October 3 – The first Waterford Crystal glassmaking business begins production in Waterford, Ireland.
- October 17 – First performance of Mozart's Great Mass
- November 2 – In Rocky Hill, New Jersey, United States General George Washington gives his Farewell Address to the Army.
- November 3 – The American Continental Army is disbanded as the first act of business by the Confederation Congress, after Thomas Mifflin is elected the new President to succeed Elias Boudinot.
- November 21 – In Paris, Jean-François Pilâtre de Rozier and François Laurent, marquis d'Arlandes, make the first untethered hot air balloon flight (flight time: 25 minutes, Maximum height: 900 m).
- November 24 – In Spain, the Cedula of Population is signed, stating that anyone who will swear fealty to Spain and is of the Roman Catholic faith is welcome to populate Trinidad and Tobago.
- November 25 – American Revolutionary War: The last British troops leave New York City and George Washington triumphantly returns, three months after the signing of the Treaty of Paris.
- November 27 – English rector John Michell concludes that some stars might have enough gravity force to prevent light escaping from them, so he calls them "dark stars".
- November 29 – 1783 New Jersey earthquake: An earthquake of 5.3 magnitude strikes New Jersey.
- December 1 – Jacques Charles and Nicolas-Louis Robert make the first manned flight in a hydrogen-filled balloon, La Charlière, in Paris.
- December 4 – At Fraunces Tavern in New York City, U.S. General George Washington formally bids his officers farewell.
- The India Act requires that the governor general be chosen from outside the British East India Company, and makes company directors subject to parliamentary supervision.
- Britain receives its first bales of imported American cotton.
- King Carlos III of the Spanish Empire authorizes land grants in Alta California.
- Princess Yekaterina Vorontsova-Dashkova is named first president of the newly created Russian Academy.
- The North Carolina General Assembly incorporates the town of Morgansborough, named for Daniel Morgan. The town is designated as the county seat for Burke County, North Carolina and is subsequently renamed Morgantown, later shortened to Morganton.
- The North Carolina General Assembly changes the name of Kingston, North Carolina, originally named for King George III of Great Britain, to Kinston.
- The Japanese famine continues as 300,000 die of starvation.
- A huge locust swarm hits South Africa.
- Foundation of the first theater in Estonia, the Tallinna saksa teater.
- Benjamin Franklin invents bifocal spectacles.
- Benjamin Franklin tries in vain to persuade the French to alter their clocks in winter to take advantage of the daylight.
- Antoine Lavoisier pioneers quantitative chemistry.
- Cholesterol is isolated.
- Carl Friedrich Gauss pioneers the field of summation with the formula summing at the age of 7.
- Madame du Coudray, pioneer of modern midwifery, retires.
- January 1 – The first issue of the Daily Universal Register, later known as The Times, is published in London.
- January 7 – Frenchman Jean-Pierre Blanchard and American John Jeffries travel from Dover, England to Calais, France in a hydrogen gas balloon, becoming the first to cross the English Channel by air.
- January 11 – Richard Henry Lee is elected as President of the U.S. Congress of the Confederation. 
- January 20 – Battle of Rạch Gầm-Xoài Mút: Invading Siamese forces, attempting to exploit the political chaos in Vietnam, are ambushed and annihilated at the Mekong River, by the Tây Sơn.
- January 27 – The University of Georgia in the United States is chartered by the Georgia General Assembly meeting in Savannah. The first students are admitted in Athens, Georgia in 1801.
- February 9 – Sir Warren Hastings, who has been governing India on behalf of King George III as the Governor-General of the Presidency of Fort William (later British India), resigns. Sir John Macpherson administers British India until General Charles Cornwallis arrives 19 months later. 
- February 27 – The Confederation Congress votes an $80,000 expense to establish diplomatic relations with Morocco. 
- March 7 – Scottish geologist James Hutton first presents his landmark work, Theory of the Earth; or an Investigation of the Laws observable in the Composition, Dissolution, and Restoration of Land upon the Globe to the Royal Society of Edinburgh. 
- General Henry Knox is appointed as the Confederation Congress's Secretary of War, with added duties as the Secretary of Navy, both functions now of the U.S. Department of Defense. 
- March 10
- April 19 – The Commonwealth of Massachusetts cedes all of its claims to territory west of New York State to the United States Confederation Congress. The area will become the southern portions of Michigan and Wisconsin. 
- April 21 – The Empress Catherine the Great of the Russian Empire issue the Charter to the Towns, providing for "a coherent, unified system of administration" for new governments organized in Russia.
- April 26 – John Adams is appointed as the U.S. ambassador to the United Kingdom, and Thomas Jefferson as ambassador to France. 
- April 28 – Astronomer William Herschel begins his second series of surveys of the stars, published in 1789. 
- May 10 – A hot air balloon crashes in Tullamore, Ireland, causing a fire that burns down about 100 houses, making it the world's first aviation disaster (by 36 days).
- May 20 – The Northwest Ordinance of 1785, setting the rules for dividing the U.S. Northwest Territory (later Ohio, Indiana, Illinois, Wisconsin and Michigan) into townships of 36 square miles apiece, is passed by the Confederation Congress. Walter G. Robillard and Lane J. Bouman, Clark on Surveying and Boundaries (LexisNexis, 1997) The survey system will later be applied to the continent west of the Mississippi River. 
- June 3 – The Continental Navy is disbanded.
- June 15 – After several attempts, Jean-François Pilâtre de Rozier and his companion, Pierre Romain, set off in a balloon from Boulogne-sur-Mer, but the balloon suddenly deflates (without the envelope catching fire) and crashes near Wimereux in the Pas-de-Calais, killing both men, making it the first fatal aviation disaster.
- October 5 – Vincenzo Lunardi of Italy becomes the first person to pilot a balloon over Scotland. 
- October 13 – The first newspaper in British India, the English-language Madras Courier, is published. It continues publication as a weekly until 1794. 
- October 13 – France mints new Louis d'or coins, with the image of King Louis XVI on the obverse, and one-sixth less gold than the coins with King Louis XV's image. 
- October 17 – The Commonwealth of Virginia stops the importation of new African slaves by declaring that "No persons shall henceforth be slaves within this commonwealth, except such as were so on the seventeenth day of October, 1785, and the descendants of the females of them." 
- October 18 – Benjamin Franklin takes office as the new President of the Supreme Council of Pennsylvania, at the time the equivalent of a republic as one of the 13 independent governments of the United States of America under the Articles of Confederation. 
- November 23 – John Hancock of Massachusetts, the former President of the Continental Congress, is selected as the new President of the Congress of the Confederation, but is unable to take office because of illness. 
- November 28 – The Treaty of Hopewell is signed between the United States of America and the Cherokee Nation.
- December 11 – An edict is issued limiting Masonic lodges throughout the Holy Roman Empire by Emperor Joseph II. With the exception of Vienna, Budapest and Prague, no Empire province may have more than one lodge. 
- July 14 – Convention of London between the Kingdom of Great Britain and the Kingdom of Spain: British settlements on the Mosquito Coast of Central America are to be evacuated; Spain expands the territory available to the British in Belize on the Yucatán Peninsula, for cutting mahogany.
- July 31 – The Kilmarnock volume of Robert Burns' Poems, Chiefly in the Scottish Dialect is published in Scotland.
- August 1 – Caroline Herschel discovers a comet (the first discovered by a woman).
- August 8 – Mont Blanc is climbed for the first time, by Dr. Michel-Gabriel Paccard and Jacques Balmat.
- August 11 – Captain Francis Light acquires the island of Penang from the Sultan of Kedah on behalf of the British East India Company, renaming it Prince of Wales Island in honour of the heir to the British throne, the first colony of the British Empire in Southeast Asia.
- August 17 – The paternal nephew of Frederick the Great, Frederick William, becomes King of Prussia, as Frederick William II.
- August 18 – The Kingdom of Denmark (including Norway) charters six settlements in Iceland to trade with it, thus ending the Danish–Icelandic Trade Monopoly, and founding Reykjavík.
- August 29 – Shays' Rebellion begins in Massachusetts.
- September–December – Goethe undertook his Italian Journey (published in 1817).
- September 2 – A hurricane strikes Barbados.
- September 11–14 – The Annapolis Convention is held by delegates from six of the 13 states (Maryland, Virginia, Pennsylvania, Delaware, New Jersey and New York) resulting in the scheduling of the Philadelphia Convention to draft a national constitution.
- September 14 – Connecticut cedes to the United States all of its claims to lands between the 41st and 42nd parallels north and west of the Connecticut Western Reserve.
- September 26 – Eden Agreement: A commercial treaty is signed between the Kingdoms of Great Britain and France.
- October 6 – HMS Bellerophon begins service with the Royal Navy.
- October 10 – The Confederation Congress of the United States directs backpay for seven months for Virginia officers who have been waiting since 1782.
- October 12 – King George III of the United Kingdom appoints Captain Arthur Phillip as the first Governor of New Holland, which comprises the area of modern Australia from the 135th meridian east to the east coast and all adjacent islands in the Pacific Ocean.
- October 16 – The Confederation Congress establishes the United States Mint to make common coinage and currency for the U.S., to replace individual state coins.
- October 23
- October 24 – General David Cobb of the Massachusetts militia defeats a body of rebel insurgents at Taunton, Massachusetts in one of the battles of Shays' Rebellion.
- November 7 – The oldest musical organization in the United States, the Stoughton Musical Society, is founded.
- November 30 – Peter Leopold Joseph of Habsburg-Lorraine, Grand Duke of Tuscany, promulgates a penal reform, making his country the first state to abolish the death penalty. November 30 is therefore commemorated by 300 cities around the world, as Cities for Life Day.
- December 4 – Mission Santa Barbara is founded by Padre Fermín Lasuén as the tenth of the Spanish missions in California.
- December 20 – Robert Burns's Address to a Haggis is first published, in Edinburgh.
- January 9 – The North Carolina General Assembly authorizes nine commissioners to purchase 100 acres (0.40 km2) of land for the seat of Chatham County. The town is named Pittsborough (later shortened to Pittsboro), for William Pitt the Younger.
- January 11 – William Herschel discovers Titania and Oberon, two moons of Uranus.
- January 19 – Mozart's Symphony No. 38 is premièred in Prague.
- February 2 – Arthur St. Clair of Pennsylvania is chosen as the new President of the Congress of the Confederation.
- February 4 – Shays' Rebellion in Massachusetts fails.
- February 21 – The Confederation Congress sends word to the 13 states that a convention will be held in Philadelphia on May 14 to revise the Articles of Confederation.
- February 28 – A charter is granted, establishing the institution which will become the University of Pittsburgh.
- March 3 – By a vote of 33 to 29, Harrisburg is approved as the new capital of the Commonwealth of Pennsylvania.
- March 17 – The Bank of North America, the central bank of the United States government under the Articles of Confederation, is re-incorporated after its charter had expired in 1786.
- March 28 – In the British House of Commons, Henry Beaufoy files the first motion to repeal the Test Act 1673, which restricts the rights of non-members of the Church of England.; Beaufoy's motion is rejected, and the Act is not repealed until 1829.
- March 30 – Biblical theology becomes a separate discipline from biblical studies, as Johann Philipp Gabler delivers his speech "On the proper distinction between biblical and dogmatic theology and the specific objectives of each" upon his inauguration as the professor of theology at the University of Altdorf in Germany.
- April 2 – A Charter of Justice is signed, providing the authority for the establishment of the first New South Wales (i.e. Australian) Courts of Criminal and Civil Jurisdiction.
- May 7 – The New Church is founded.
- May 13 – Captain Arthur Phillip leaves Portsmouth, England with the 11 ships of the First Fleet, carrying around 700 convicts and at least 300 crew and guards, to establish a penal colony in Australia.
- May 14 – In Philadelphia, delegates begin arriving for a Constitutional Convention.
- May 22 – In Britain, Thomas Clarkson and Granville Sharp found the Society for Effecting the Abolition of the Slave Trade, with support from John Wesley, Josiah Wedgwood and others.
- May 25 – In Philadelphia, delegates begin to convene the Constitutional Convention, intended to amend the Articles of Confederation (however, a new United States Constitution is eventually produced). George Washington presides over the Convention.
- May – Orangist troops attack Vreeswijk, Harmelen and ; civil war starts in the Dutch Republic.
- May 31 – The original Lord's Cricket Ground in London holds its first cricket match; Marylebone Cricket Club founded.
- June 20 – Oliver Ellsworth moves at the Federal Convention that the government be called the United States.
- June 28 – Princess Wilhelmina of Orange, sister of King Frederick William II of Prussia, is captured by Dutch Republican patriots, taken to Goejanverwellesluis and not allowed to travel to The Hague.
- October 1 – Russo-Turkish War (1787–92) – Battle of Kinburn: Alexander Suvorov, though sustaining a wound, routs the Turks.
- October 27 – The first of The Federalist Papers, a series of essays calling for ratification of the U.S. Constitution, is published in The Independent Journal, a New York newspaper.
- October 29 – Wolfgang Amadeus Mozart's opera Don Giovanni (libretto by Lorenzo Da Ponte) premieres in the Estates Theatre in Prague.
- November 1 – The first secondary education school open to girls in Sweden, Societetsskolan, is founded in Gothenburg.
- November 21 – Treaty of Versailles (1787) signed, forming an alliance between the Kingdom of France and the Lord Nguyễn Phúc Ánh, future Emperor of Vietnam.
- December 3 – James Rumsey demonstrates his water-jet propelled boat on the Potomac River.
- December 7 – Delaware ratifies the Constitution, and becomes the first U.S. state.
- December 8 – La Purisima Mission is founded by Padre Fermín Lasuén as the eleventh of the Spanish missions in California.
- December 12 – Pennsylvania becomes the second U.S. state.
- December 18 – New Jersey becomes the third U.S. state.
- December 23 – Captain William Bligh sets sail from England for Tahiti, in HMS Bounty.
- January 1 – The first edition of The Times, previously The Daily Universal Register, is published in London.
- January 2 – Georgia ratifies the United States Constitution, and becomes the fourth U.S. state under the new government.
- January 9 – Connecticut ratifies the United States Constitution, and becomes the fifth U.S. state.
- January 18 – The leading ship (armed tender HMS Supply) in Captain Arthur Phillip's First Fleet arrives at Botany Bay, to colonise Australia.
- January 22 – the Congress of the Confederation, effectively a caretaker government until the United States Constitution can be ratified by at least nine of the 13 states, elects Cyrus Griffin as its last president. 
- January 24 – The La Perouse expedition in the Astrolabe and Boussole arrives off Botany Bay, just as Captain Arthur Phillip is attempting to move his colony from there to Sydney Cove in Port Jackson.
- January 26 – Australia Day: Eleven ships of the First Fleet from Botany Bay, led by Captain Arthur Phillip, land at Sydney Cove (which will become Sydney), Australia, where he determines to establish the British prison colony of New South Wales, the first permanent European settlement on the continent.
- January 31 – Henry Benedict Stuart becomes the new Stuart claimant to the throne of Great Britain, as King Henry IX and the figurehead of Jacobitism.
- February 1 – Isaac Briggs and William Longstreet patent a steamboat.
- February 6 – Massachusetts ratifies the United States Constitution, and becomes the sixth U.S. state.
- February 7 – Sydney is named and founded, by the British Colony of New South Wales.
- February 9 – Austria enters the Russo-Turkish War (1787–92), and attacks Moldavia.
- February 17 – The uninhabited Lord Howe Island is discovered by the brig HMS Supply, commanded by Lieutenant Ball, who is on his way from Botany Bay to Norfolk Island with convicts to start a penal settlement there. They arrive at Norfolk Island on March 6.
- March 10 – The La Perouse expedition leaves Sydney Cove for New Caledonia, never to be seen again.
- March 14 – The Edinburgh Evening Courant carries a notice of £200 reward for the capture of William Brodie, a town councilor doubling as a burglar.
- March 21 – The Great New Orleans Fire kills 25% of the population and destroys 856 buildings, including St. Louis Cathedral and The Cabildo, leaving most of the town in ruins.
- April 7 – American pioneers establish the town of Marietta (in modern-day Ohio), the first permanent American settlement outside the original Thirteen Colonies.
- April 13 – America's first recorded riot, the 'Doctors' Mob', begins. Residents of Manhattan are angry about grave robbers stealing bodies for doctors to dissect. The rioting is suppressed on April 15.
- April 28 – Maryland ratifies the United States Constitution, and becomes the seventh U.S. state.
- May 10 – The Royal Dramatic Theatre (Kungliga Dramatiska Teatern), Sweden's national drama company, is founded.
- May 15 – The Australian frontier wars begin.
- May 23 – South Carolina ratifies the United States Constitution, and becomes the eighth U.S. state.
- June 7 – France: Day of the Tiles, which some consider the beginning of the French Revolution.
- June 9 – The African Association, an exploration group dedicated to plotting the Niger River and finding Timbuktu, is founded in England.
- June 17 – English captains Thomas Gilbert and John Marshall, returning from Botany Bay, become the first Europeans to encounter the Gilbert Islands in the Pacific Ocean. They also chart islands in "Lord Mulgrove's range", later known as the Marshall Islands.
- June 21 – New Hampshire ratifies the United States Constitution, and becomes the ninth U.S. state, enabling the Constitution to go into effect. (The latter happens on March 4, 1789, when the first Congress elected under the new Constitution assembles.)
- June 25 – The Virginia Ratifying Convention ratifies the United States Constitution, and becomes the tenth U.S. state under the new government.
- June 26 – Wolfgang Amadeus Mozart, in Vienna, completes his antepenultimate symphony, now called the Symphony No. 39 in E-flat.
- July 13 – A hailstorm sweeps across France and the Dutch Republic, with hailstones 'as big as quart bottles' that take 'three days to melt'; immense damage is done.
- July 24 – Governor General Lord Dorchester, by proclamation issued from the Chateau St. Louis in Quebec City, divides the British Province of Quebec into five Districts, namely: Gaspé, Nassau, Lunenburg, Mecklenburg, and Hesse.
- July 26 – New York ratifies the United States Constitution, and becomes the eleventh U.S. state.
- July 28 – Wolfgang Amadeus Mozart, in Vienna, completes his penultimate symphony, now called the Symphony No. 40 in G Minor.
- August 8 – King Louis XVI of France agrees to convene the Estates-General meeting in May 1789, the first time since 1614.
- August 10 – Wolfgang Amadeus Mozart, in Vienna, completes his final symphony, now called the Symphony No. 41 in C Major, and nicknamed (after his death) The Jupiter.
- August 27 – The trial of Deacon William Brodie for burglary begins in Edinburgh, Scotland; he is sentenced to death by hanging.
- September 13 – The United States Congress of the Confederation passes an act providing a timeline for the voting for the first President under the new U.S. Constitution. 
- September 21 – Austro-Turkish War - Battle of Karánsebes: The Austrian army engages in a friendly-fire incident, which results in mass casualties.
- September 24 – The Theater War begins, when the army of Denmark–Norway invades Sweden.
- Annual British iron production reaches 68,000 tons.
- 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.
- February – King Gustav III of Sweden enforces the Union and Security Act, delivering the coup de grace to Sweden's 70-year-old parliamentarian system, in favor of absolute monarchy.
- February 4 – George Washington is unanimously elected the first President of the United States, by the United States Electoral College.
- March – The first version of a graphic description of a slave ship (the Brookes) is issued on behalf of the English Society for Effecting the Abolition of the Slave Trade.
- March 4 – At Federal Hall in New York City, the 1st United States Congress meets, and declares the new United States Constitution to be in effect. The bicameral United States Congress replaces the unicameral Congress of the Confederation, as the legislature of the federal government of the United States.
- March 11 – The Venetian arsenal on the island of Corfu, containing 72,000 pounds (33,000 kg) of gunpowder and 600 bombshells, explodes during a fire, killing 180 bystanders and knocking down a seawall.
- 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
- 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.
- Famine in Ethiopia.
- 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.