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was a common year starting on Tuesday of the Gregorian calendar and a common year starting on Saturday of the Julian calendar, the 1799th year of the Common Era (CE) and Anno Domini (AD) designations, the 799th year of the 2nd millennium, the 99th year of the 18th century, and the 10th and last year of the 1790s decade. As of the start of 1799, the Gregorian calendar was
11 days ahead of the Julian calendar, which remained in localized use until 1923.
- January 9 – British Prime Minister William Pitt the Younger introduces an income tax of two shillings to the pound, to raise funds for Great Britain's war effort in the Napoleonic Wars.
- January 17 – Maltese patriot Dun Mikiel Xerri, along with a number of other patriots, is executed.
- February 9 – Quasi-War: In the single-ship action of USS Constellation vs L'Insurgente in the Caribbean, the American ship is the victor.
- February 28 – French Revolutionary Wars: Action of 28 February 1799 – British Royal Navy frigate HMS Sybille defeats the French frigate Forte, off the mouth of the Hooghly River in the Bay of Bengal, but both captains are killed.
- March 1 – Federalist James Ross becomes President pro tempore of the United States Senate.
- March 4 – The Russo-Ottoman siege of Corfu ends with the surrender of the French garrison, bringing an end to the first period of French rule in the Ionian Islands.
- March 7 – Siege of Jaffa: Napoleon captures Jaffa, Palestine, and his troops proceed to kill more than 2,000 Albanian captives.
- March 29 – New York passes a law aimed at gradually abolishing slavery in the state.
- April 27 – French Revolutionary Wars: The Battle of Cassano takes place outside of Milan, as Russian and Austrian troops commanded by General Alexander Suvorov rout the French Army under the command of General Jean Moreau.
- May 4 – Battle of Seringapatam: Tipu Sultan is defeated and killed by the British; the captivity of Mangalorean Catholics at Seringapatam ends.
- May 21 – The Siege of Acre ends after two months; Napoleon's attempt to widen his Middle Eastern campaign into Syria is frustrated by Ottoman forces, and he withdraws to Egypt.
- May 27 – Battle of Winterthur: Habsburg forces secure control of north-east Switzerland, from the French Army of the Danube.
- June 18 – French Revolutionary Wars: Action of 18 June 1799 – A French frigate squadron, under Rear-admiral Perrée, is captured by the British fleet under Lord Keith, off Toulon.
- July 7 – Ranjit Singh's men take their positions outside Lahore.
- July 12 – Ranjit Singh captures Lahore from the Bhangi Misl, a key step in establishing the Sikh Empire, and becoming Maharaja of the Punjab.
- July 15 – In the Egyptian port city of Rosetta, French Captain Pierre Bouchard finds the Rosetta Stone.
- July 25 – At Aboukir, Egypt, Napoleon defeats 10,000 Ottoman Mamluk troops under Mustafa Pasha.
- August 27 – War of the Second Coalition – Anglo-Russian invasion of Holland: Britain and Russia send an expion to the Batavian Republic.
- August 29 – Pope Pius VI, at the time the longest reigning Pontiff of the Roman Catholic Church, dies as a prisoner of war in the citadel of the French city of Valence, after 24½ years of rule.
- August 30 – Anglo-Russian invasion of Holland – Vlieter Incident: A squadron of the Batavian Republic's navy, commanded by Rear-Admiral Samuel Story, surrenders to the British Royal Navy, under Sir Ralph Abercromby and Admiral Sir Charles Mitchell, near Wieringen, without joining action.
- September 23 – Frederick North, 5th Earl of Guilford, the Governor of British Ceylon (now Sri Lanka, issues a proclamation declaring that the laws of the Netherlands for the conquered Dutch Ceylon shall be enforced until superseded by new laws. 
- September 29 – the Second Roman Republic, a puppet state formed by the French Army after their dissolution of the Papal States and the occupation of Rome, is dissolved 19 months after its creation on February 15, 1798. 
- October 6 – Anglo-Russian invasion of Holland – Battle of Castricum: Franco-Dutch forces defeat the Russo-British expion force.
- October 9 – HMS Lutine (a famous treasure wreck) is sunk in the West Frisian Islands.
- October 12 – Jeanne Geneviève Labrosse becomes the first woman to jump from a balloon with a parachute, from an altitude of 900 metres (3,000 ft).
- October 16 – Action of 16 October 1799: A Spanish treasure convoy worth more than £54,000,000 is captured by the British Royal Navy off Vigo.
- October 18 – Anglo-Russian invasion of Holland: Anglo-Russian expion forces surrender in North Holland.
- November 9 (Coup of 18 Brumaire) – Napoleon overthrows the French Directory in a coup d'état, which ends the French Revolution.
- November 10 (19 Brumaire) – A remnant of the Council of Ancients in France abolishes the Constitution of the Year III, and ordains the French Consulate with Napoleon as First Consul, with the Constitution of the Year VIII.
- December 3 – War of the Second Coalition: Battle of Wiesloch: Austrian Lieutenant Field Marshal Anton Sztáray defeats the French at Wiesloch.
- December 10 – France adopts the metre as its official unit of length.
- December 14 – George Washington, first President of the United States, dies at Mount Vernon, Virginia.
- December 31 – The Dutch East India Company's charter is allowed to expire by the Batavian Republic.
- The Place Royale in Paris is renamed Place des Vosges, when the Department of Vosges becomes the first to pay new Revolutionary taxes.
- Eli Whitney, holding a 1798 United States government contract for the manufacture of muskets, is introduced by Oliver Wolcott, Jr. to the concept of interchangeable parts, an origin of the American system of manufacturing.
- Conrad John Reed, 12, finds what he describes as a "heavy yellow rock" along Little Meadow Creek in Cabarrus County, North Carolina, and makes it a doorstop in his home. Conrad's father John Reed learns that the rock is actually gold in 1802, initiating the first gold rush in the United States.
- The assassination of the 14th Tu'i Kanokupolu, Tukuʻaho, plunges Tonga into half a century of civil war.
- The Nawab (provincial governor) of Oudh in northern India sends to George III of England the Padshah Nama, an official history of the reign of Shah Jahan.
- William Cockerill begins building cotton-spinning equipment in Belgium.
- The small town of Tignish, Prince Edward Island, Canada is founded.
- January 6 – Jedediah Smith, American fur trapper, explorer (d. 1831)
- January 12 – Priscilla Susan Bury, British botanist (d. 1872)
- January 23 – Alois Negrelli, Tyrolean engineer, railroad pioneer active in the Austrian Empire (1858)
- January 31 – Rodolphe Töpffer, Swiss teacher, author, and artist (d. 1846)
- February 4 – Almeida Garrett, Portuguese writer (d. 1854)
- February 11 – Basil Moreau, founder of the Congregation of Holy Cross (d. 1873)
- February 14 – Walenty Wańkowicz, Polish painter (d. 1842)
- February 27 – Edward Belcher, British admiral (d. 1877)
- March 8 – Simon Cameron, American politician (d. 1889)
- March 16 – Anna Atkins, British botanist (d. 1871)
- March 20 – Karl August Nicander, Swedish poet (d. 1839)
- March 22 – Friedrich Wilhelm Argelander, German astronomer (d. 1875)
- March 28 – Karl Adolph von Basedow, German physician, noted for reporting the symptoms of Graves–Basedow disease (d. 1854)
- March 29 – Edward Smith-Stanley, 14th Earl of Derby, Prime Minister of the United Kingdom (d. 1869)
- April 12 – Henri Druey, Swiss Federal Councilor (d. 1855)
- April 17 – Eliza Acton, English poet and cookery writer (d. 1859)
- May 13 – Catherine Gore, English author (d. 1861)
- May 20 – Honoré de Balzac, French author (d. 1850)
- May 21 – Mary Anning, British paleontologist (d. 1847)
- May 25 – Alexei Lvov, Russian composer (d. 1870)
- June 3 – Elisabetta Fiorini Mazzanti, Italian botanist (d. 1879)
- June 6 – Alexander Pushkin, Russian author (d. 1837)
- June 18 – Prosper Ménière, French physician (d. 1862)
- June 23 – Charlotte Birch-Pfeiffer, German actress, writer and theater director (d. 1868)
- June 25 – David Douglas, Scottish-born botanist (d. 1834)
- July 4 – King Oscar I of Sweden and Norway (d. 1859)
- July 6 – Michael Thomas Bass, English brewer (d. 1884)
- August 12 – Patrick MacDowell, Irish sculptor (d. 1870)
- September 8 – James Bowman Lindsay, Scottish inventor (d. 1862)
- September 10 – George Willison Adams, American abolitionist (d. 1879)
- October 1 – John Brown Russwurm, American abolitionist (d. 1851)
- October 18 – Christian Friedrich Schönbein, German chemist (d. 1868)
- October 26 – Margaret Agnes Bunn, British actress (d. 1883)
- November 1 – Thomas Baldwin Marsh, American religious leader (d. 1866)
- November 7 – James Syme, Scottish medical reformer (d. 1870)
- November 29 – Amos Bronson Alcott, father of novelist Louisa May Alcott (d. 1888)
- December 3 – Peggy Eaton, wife of Secretary of State John Eaton (central character of the Petticoat affair) (d. 1879)
- December 25 – Augusta Hejnek, last surviving person from the 1700s (d. 1908)
- January 9 – Maria Gaetana Agnesi, Italian mathematician (b. 1718)
- January 22 – Horace-Bénédict de Saussure, Swiss aristocrat, alpinist (b. 1740)
- February 6 – Étienne-Louis Boullée, French architect (b. 1728)
- February 7 – Qianlong Emperor of China (b. 1711)
- February 12 – Lazzaro Spallanzani, Italian biologist, physiologist (b. 1729)
- February 16 – Charles Theodore, Elector of Bavaria (b. 1724)
- February 19 – Jean-Charles de Borda, French mathematician, physicist, political scientist, and sailor (b. 1733)
- February 22 – Heshen, Manchu official under Qianlong (b. 1750)
- February 24 – Georg Christoph Lichtenberg, German scientist, satirist, and Anglophile (b. 1742)
- March 17 – Sir Charles Thompson, 1st Baronet, British admiral, politician (b. c. 1740)
- March 28 – Etta Palm d'Aelders, Dutch-French feminist (b. 1743)
- March 29 – Helena Dorothea von Schönberg, German industrialist (d. 1729)
- April 3 – Pierre Charles Le Monnier, French astronomer (b. 1715)
- April 6 – Alexander Bezborodko, Grand Chancellor of Russia, architect of Catherine the Great's foreign policy (b. 1747)
- May 2 – Guemes Padilla Horcasitas, the Viceroy of New Spain (b. 1740)
- May 4 – Tipu Sultan, Indian ruler (b. 1750)
- May 18 – Pierre Beaumarchais, French writer (b. 1732)
- May 26 – James Burnett, Lord Monboddo, Scottish jurist (b. 1714)
- June 6 – Patrick Henry, American revolutionary politician, Governor of Virginia (b. 1736)
- June 10 – Chevalier de Saint-Georges, Guadeloupe-born French musician (b. 1745)
- June 30 – Francesco Caracciolo, Neapolitan admiral, revolutionist (b. 1752)
- July 7 – William Curtis, English botanist, entomologist (b. 1746)
- August 2 – Jacques Étienne Montgolfier, French inventor of the hot-air balloon, balloonist (b. 1744)
- August 4 – John Bacon, British sculptor (b. 1740)
- August 5 – Richard Howe, British admiral (b. 1726)
- August 15 – Barthélemy Catherine Joubert, French general (b. 1769)
- August 20 – Eleonora de Fonseca Pimentel, Italian poet, journalist and revolutionary (b. 1752)
- August 29 – Pope Pius VI (b. 1717)
- August 31 – Nicolas-Henri Jardin, French architect (b. 1720)
- September 7 – Jan Ingenhousz, Dutch physician, physiologist, biologist, and chemist (b. 1730)
- October 6 – William Withering, British physician (b. 1741)
- October 9 – Pierre Pigneau de Behaine, French priest who helped to establish the Nguyễn dynasty (b. 1741)
- October 24 – Carl Ditters von Dittersdorf, Austrian composer (b. 1739)
- November 22 – Judith van Dorth, Dutch orangist (b. 1747)
- December 6 – Joseph Black, Scottish physician, physicist, and chemist (b. 1728)
- December 14 – George Washington, military leader of the American Revolution, president of the Constitutional Convention (1787), and the 1st President of the United States (b. 1732)
- December 31 – Jean-François Marmontel, French historian, writer (b. 1723)
- ^ "Historical Events for Year 1799 | OnThisDay.com". Historyorb.com. Retrieved 2016-07-11.
- ^ T. Nadaraja, The Legal System of Ceylon in Its Historical Setting (E. J. Brill, 1972) p181
- ^ "The Protagonists and the Principal Phases of the Roman Republic of 1798 to 1799", by Marina Formica, in Tosca's Prism: Three Moments of Western Cultural History, ed. by Deborah Burton, et al. (Northeastern University Press, 2004) p67
- ^ Woodbury, Robert S. (1960). "The Legend of Eli Whitney and Interchangeable Parts". Technology and Culture. 1.