- January 4 – Constantine Hangerli enters Bucharest, as Prince of Wallachia.
- January 22 – A coup d'état is staged in the Netherlands (Batavian Republic). Unitarian Democrat Pieter Vreede ends the power of the parliament (with a conservative-moderate majority).
- February 10 – The papacy is removed from power, by French General Louis-Alexandre Berthier.
- February 15— U.S. Representative Roger Griswold (Fed-CT) beats Congressman Matthew Lyon (Rep-VT) with a cane after the House declines to censure Lyon earlier spitting in Griswold's face; the House declines to discipline either man. 
- March 5 – French troops enter Bern.
- March 7 – French forces invade the Papal States, and establish the Roman Republic.
- April 7 – The Mississippi Territory is organized by the United States, from territory ceded by Georgia and South Carolina; later it is twice expanded, to include disputed territory claimed by both the U.S. and Spain (which acquired territory in trade with Great Britain). 
- April 12 – The Helvetic Republic, a French client republic, is proclaimed following the collapse of the Old Swiss Confederacy, after the French invasion.
- April 26 – France annexes Geneva.
- April 30— The United States Department of the Navy is established as a cabinet-level department. Benjamin Stoddert, a civilian businessman, is appointed as the first Navy Secretary by President Adams. 
- May 9 – Napoleon sets off for Toulon, and sails aboard Vice-Admiral Brueys's flagship L'Orient; his squadron is part of a larger fleet of over 300 vessels, carrying almost 37,000 troops.
- May 23 – Irish republicans and nationalists, known as the Society of United Irishmen, launch a rebellion against British rule, in expectation of greater support from France, which only sends 1,100 men. The United Irishmen are unique amongst Irish nationalist movements, in that they unify Catholics and Protestants around republican ideals. The rebellion rages sporadically, but is defeated by the British by October.
- June 6
- The platypus was first discovered by Europeans.
- January 14 – Johan Rudolph Thorbecke, Dutch politician (d. 1872)
- January 19 – Auguste Comte, French sociologist (d. 1857)
- January 20 – Anson Jones, 5th and last President of the Republic of Texas (d. 1858)
- March 9 – Mathilda Berwald, Finnish and Swedish concert singer (d. 1877)
- March 25 – Christoph Gudermann, German mathematician (d. 1852)
- March 25 – Corvo Attano, fictional character, Royal Protector, assassin (d. unknown)
- March 13 – Abigail Fillmore, First Lady of the United States (d. 1853)
- April 2 – August Heinrich Hoffmann von Fallersleben, German writer (d. 1874)
- April 3 – Charles Wilkes, American naval officer, explorer (d. 1877)
- April 12 – Baron du Potet, French writer (d. 1881)
- April 26 – Eugène Delacroix, French painter (d. 1863)
- April 28 – Duncan Forbes, British linguist (d. 1868)
- May 10 – Christodoulos Hatzipetros, Greek military leader (d. 1869)
- June 12 – William Abbot, English actor (d. 1843)
- June 14 – František Palacký, Czech historian, politician (d. 1876)
- June 29 – Giacomo Leopardi, Italian writer (d. 1837)
- July 15 – Alexander Gorchakov, Russian politician (d. 1883)
- August 17 – Thomas Hodgkin, British physician, pathologist (d. 1866)
- September 4 – Raynold Kaufgetz, Swiss academic (d. 1869)
- September 11 – Franz Ernst Neumann, German mineralogist, physicist and mathematician (d. 1895)
- October 2 – King Charles Albert of Sardinia (d. 1849)
- February 12 – Stanisław August Poniatowski, deposed last King of Poland and Grand Duke of Lithuania (b. 1732)
- February 25 – Louis Jules Mancini Mazarini, French diplomat, writer (b. 1716)
- March 22 – Justin Morgan, American horse breeder and composer (b. 1747)
- April 11 – Karl Wilhelm Ramler, German poet (b. 1725)
- April 12 – Madeleine de Puisieux, French writer, active feminist (b. 1720)
- April 14 – Henry Mowat, Scottish-born British Royal Navy officer (b. 1734)
- April 29 – Nikolaus Poda von Neuhaus, German entomologist (b. 1723)
- May 10 – George Vancouver, British Royal Navy officer, explorer (Vancouver, Canada is named after him) (b. 1757)
- May 19 – William Byron, 5th Baron Byron, English dueler (b. 1722)
- June – Betsy Gray, Irish rebel, heroine
- June 4 – Giacomo Casanova, Italian adventurer, writer (b. 1725)
- June 21 – John Kelly of Killanne, Irish republican
- June 25 – Thomas Sandby, English cartographer, architect (b. 1721)
- July 17 – Henry Joy McCracken, Irish republican
- July 21 – François Sébastien Charles Joseph de Croix, Count of Clerfayt, Austrian field marshal (b. 1733)
- August 1 – François-Paul Brueys d'Aigalliers, French admiral (killed in battle) (b. 1753)
- August 18 – John Lewis Gervais, American revolutionary, member of Provincial Congress (1775), State’s Committee of Safety (1775-1781), South Carolina Senate (1781, 1782), Continental Congress (1782, 1783) (b. 1741)
- August 21 – James Wilson, American politician (b. 1742)
- August 24 – Thomas Alcock, English clergyman (b. 1709)
- August 25 – Mikiel'Ang Grima, Maltese surgeon (b. 1731)
- September 21 – George Read, American lawyer, signer of the Declaration of Independence (b. 1733)
- November 19 – Theobald Wolfe Tone, Irish republican (b. 1737)
- December 4 – Luigi Galvani, Italian physicist (b. 1763)
- Wang Cong'er, Chinese rebel leader (b. 1777)