|Centuries:||17th century – 18th century – 19th century|
|Decades:||1760s 1770s 1780s – 1790s – 1800s 1810s 1820s|
|Years:||1795 1796 1797 – 1798 – 1799 1800 1801|
|1798 by topic:|
|Arts and Sciences|
|Archaeology – Architecture – Art – Literature (Poetry) – Music – Science|
|Australia – Canada –Denmark – France – Great Britain – Ireland – Norway – Portugal – Russia – Scotland –Sweden – United States|
|Lists of leaders|
|Colonial governors – State leaders|
|Birth and death categories|
|Births – Deaths|
|Establishments and disestablishments categories|
|Establishments – Disestablishments|
|French Republican calendar||6–7|
|Ab urbe condita||2551|
|British Regnal year||38 Geo. 3 – 39 Geo. 3|
|Chinese calendar||丁巳年 (Fire Snake)
4494 or 4434
— to —
戊午年 (Earth Horse)
4495 or 4435
|- Vikram Samvat||1854–1855|
|- Shaka Samvat||1719–1720|
|- Kali Yuga||4898–4899|
|Japanese calendar||Kansei 10
|Julian calendar||Gregorian minus 11 days|
|Minguo calendar||114 before ROC
|Thai solar calendar||2340–2341|
|Wikimedia Commons has media related to 1798.|
1798 (MDCCXCVIII) was a common year starting on Monday (dominical letter G) of the Gregorian calendar and a common year starting on Friday (dominical letter C) of the Julian calendar, the 1798th year of the Common Era (CE) and Anno Domini (AD) designations, the 798th year of the 2nd millennium, the 98th year of the 18th century, and the 9th year of the 1790s decade. As of the start of 1798, the Gregorian calendar was 11 days ahead of the Julian calendar, which remained in localized use until 1918.
- January 22 – A coup d'état is staged in the Netherlands (Batavian Republic). Unitarian Democrat Pieter Vreede makes an end to the power of the parliament (with a conservative-moderate majority).
- February 10 – The papacy is removed from power by French General Louis-Alexandre Berthier.
- 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 – Helvetic Republic, a French client republic, proclaimed following collapse of the Old Swiss Confederacy on French invasion.
- April 26 – France annexes Geneva.
- May 9 – Napoleon sets off for Toulon, and sails aboard Vice-Admiral Brueys's flagship L'Orient, his squadron 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 sent 1100 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 12
- June 13 – Mission San Luis Rey de Francia is founded.
- July 1 – Egyptian Campaign: Napoleon disembarks his French army in Marabout Bay.
- July 7
- July 11 – The United States Marine Corps is re-established.
- July 12 – Battle of Shubra Khit between French and Mamelukes, during Napoleon's march from Alexandria to take Cairo.
- July 14 – The Alien and Sedition Acts become United States law, making it a federal crime to write, publish, or utter false or malicious statements about the United States government.
- July 16 – The Relief of Sick and Disabled Seamen Act is signed into law, creating the Marine Hospital Service, the forerunner to the current United States Public Health Service Commissioned Corps.
- July 21 – Battle of the Pyramids: Napoleon defeats Ottoman forces near the Pyramids.
- July 24 – Napoleon occupies Cairo.
- July 31 – A second round of elections are held in the Netherlands (Batavian Republic); no general elections this time.
- August 1 – Battle of the Nile (near Abu Qir): Lord Nelson defeats the French navy under Admiral Brueys; Nelson himself is wounded in the head.
- August 22 – French troops land at Kilcummin in County Mayo to assist the Irish rebellion.
- September – Charles Brockden Brown publishes the first significant American novel, the Gothic fiction Wieland: or, The Transformation; an American Tale.
- September 10 – Battle of St. George's Caye: Off the coast of British Honduras (now Belize), a group of British nationals and African slaves defeat a force sent from Mexico to drive them out.
- September 18 – Lyrical Ballads is published anonymously by Samuel Taylor Coleridge and William Wordsworth, inaugurating the English Romantic movement in literature.
- October 12 – Battle of Tory Island: A British Royal Navy squadron under Sir John Borlase Warren prevents French Republican ships commanded by Jean-Baptiste-François Bompart landing reinforcements for the Society of United Irishmen on the Donegal coast; Irish leader Wolfe Tone is captured and later dies of wounds.
- November 4 – Beginning of the Russo-Ottoman siege of Corfu.
- November 8 – British whaler John Fearn becomes the first European to land on Nauru.
- The first (anonymous) publication occurs of An Essay on the Principle of Population by Thomas Malthus.
- Aarau becomes the temporary capital of the Helvetic Republic.
- Alois Senefelder invents lithography.
- Eli Whitney contracts with the U.S. federal government for 10,000 muskets, which he produces with interchangeable parts.
- The first census in Brazil counts 2 million blacks in a total population of 3.25 million.
- The Ayrshire (Earl of Carrick's Own) Yeomanry, a British Army Yeomanry Cavalry Regiment, formed by The Earl of Cassillis at Culzean Castle, Ayrshire in 1794, is adopted onto the British Army List.
- Jenner publishes his work on smallpox vaccination
- 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 25 – Christoph Gudermann, German mathematician (d. 1852)
- March 13 – Abigail Fillmore, First Lady of the United States (d. 1853)
- April 2 – August Heinrich Hoffmann von Fallersleben, German writer (d. 1874)
- 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 and politician (d. 1876)
- June 29 – Giacomo Leopardi, Italian writer (d. 1837)
- August 17 – Thomas Hodgkin, British physician and 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)
- October 12 – Pedro I, Emperor of Brazil (also Pedro IV, King of Portugal) (d. 1834)
- December 24 – Adam Mickiewicz, Polish writer (d. 1855)
- February 25 – Louis Jules Mancini Mazarini, French diplomat and writer (b. 1716)
- March 22 – Justin Morgan, American horse breeder and composer (b. 1747)
- April 11 – Karl Wilhelm Ramler, German poet (b. 1725)
- April 14 – Henry Mowat, Scottish-born Royal Navy officer (b. 1734)
- April 29 – Nikolaus Poda von Neuhaus, German entomologist (b. 1723)
- May 19 – William Byron, 5th Baron Byron, English dueler (b. 1722)
- June 4 – Giacomo Casanova, Italian adventurer and writer (b. 1725)
- June 21 – John Kelly of Killanne, Irish republican
- June 25 – Thomas Sandby, English cartographer and 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 from 1775 to 1781, South Carolina’s Senate in 1781 and 1782, Continental Congress 1782 and 1783; died in Charleston, S.C. (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 and 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)