|Centuries:||18th century – 19th century – 20th century|
|Decades:||1770s 1780s 1790s – 1800s – 1810s 1820s 1830s|
|Years:||1802 1803 1804 – 1805 – 1806 1807 1808|
|1805 in topic:|
|Archaeology – Architecture – Art – Literature – Music|
|Australia – Brazil - Canada – Denmark - France – Germany – Mexico – Norway - Philippines - Portugal– South Africa – Spain - Sweden - United Kingdom – United States|
|Rail Transport – Science – Sports|
|Lists of leaders|
|Colonial Governors – State leaders|
|Birth and death categories|
|Births – Deaths|
|Establishments and disestablishments categories|
|Establishments – Disestablishments|
|French Republican calendar||13–14|
|Ab urbe condita||2558|
|British Regnal year||45 Geo. 3 – 46 Geo. 3|
|Chinese calendar||甲子年 (Wood Rat)
4501 or 4441
— to —
乙丑年 (Wood Ox)
4502 or 4442
|- Vikram Samvat||1861–1862|
|- Shaka Samvat||1727–1728|
|- Kali Yuga||4906–4907|
|Japanese calendar||Bunka 2
|Julian calendar||Gregorian minus 12 days|
|Minguo calendar||107 before ROC
|Thai solar calendar||2347–2348|
|Wikimedia Commons has media related to 1805.|
Year 1805 (MDCCCV) was a common year starting on Tuesday (link will display the full calendar) of the Gregorian calendar and a common year starting on Sunday of the 12-day slower Julian calendar. After thirteen years the French First Empire abolished the French Republican Calendar in favour of the Gregorian calendar.
- January 11 – Michigan Territory is created.
- February 15 – The Harmony Society is officially formed as a Christian community in Harmony, Pennsylvania.
- March 1 – Justice Samuel Chase is acquitted of impeachment charges by the United States Senate.
- March 4 – Thomas Jefferson is sworn in for a second term as President of the United States.
- March 5 – The New Brunswick Legislature passes a bill to advance literacy in the province, which eventually leads to the creation of public education in what is now Canada.
- April 7 – Beethoven's Symphony No. 3, Eroica, has its public premiere at the Theater an der Wien in Vienna under his baton.
- April 27 – Battle of Derne: United States Marines and Berbers attack the Tripolitan city of Derna (the "Shores of Tripoli").
- April 29 – Rutger Jan Schimmelpenninck is appointed as Grand Pensionary of the Batavian Republic by Napoleon.
- May 26 – Napoleon is crowned King of Italy.
- May 31–June 2 – Napoleonic Wars – Battle of Diamond Rock: A Franco-Spanish fleet captures the strategic island of Diamond Rock off Martinique in the West Indies from the British occupying force.
- June 1 – Tuscan-born composer Luigi Boccherini is buried in St. Michael's Basilica, Madrid, after being found dead on May 28.
- June 4 – The First Barbary War ends between Tripoli and the United States of America.
- June 4
- June 13 – Lewis and Clark Expedition in the United States: Scouting ahead of the expedition, Meriwether Lewis and four companions sight the Great Falls of the Missouri River, confirming they are heading in the right direction.
- July 9 – Muhammad Ali Pasha founds his dynasty in Egypt.
- July 26 – An earthquake killed 5,573 people in Molise and Campania, Italy
- October 17 – Napoleonic Wars
- October 21 – Napoleonic Wars – Battle of Trafalgar: British naval fleet led by Admiral Horatio Nelson defeats a combined French and Spanish fleet off the coast of Spain; however, Admiral Nelson is fatally shot.
- November 7 – The Lewis and Clark Expedition arrives at the Pacific Ocean.
- November 11 – Napoleonic Wars – Battle of Dürenstein: 8,000 French troops attempt to slow the retreat of a vastly superior Russian and Austrian force.
- November 16 – Napoleonic Wars – Battle of Schöngrabern: Russian forces under Pyotr Bagration delay the pursuit by French troops under Joachim Murat.
- November 20 – Beethoven's only opera Fidelio in its original form (known retrospectively as Leonore) is premiered at the Theater an der Wien in Vienna, which at this time is under French military occupation.
- November 26 – The Pontcysyllte Aqueduct is opened in Wales; it is 1,007 ft (307 m) long and 126 ft (38 m) tall.
- December 2 – Napoleonic Wars – Battle of Austerlitz: French troops under Napoleon decisively defeat a joint Russo-Austrian force.
- December 26 – The Peace of Pressburg is signed between France and Austria.
- King Anouvong becomes ruler of Vientiane.
- Napoleon annuls the 10-day week of the French Republican Calendar with effect from 1 January 1806 (the day after 10 Nivôse an XIV); he also orders his soldiers to be vaccinated.
- Sweden declares war on France.
- The Horse Patrol, a mounted law enforcement force, is founded in London, England.
- James Squire becomes the first person in Australia to cultivate Hops.
- Old Man of the Mountain is first mentioned.
- January 8 – Orson Hyde, American religious leader (d. 1878)
- January 27 – Samuel Palmer, English artist (d. 1881)
- February 18 – Louis M. Goldsborough, United States Navy admiral (d. 1877)
- March 3 – Jonas Furrer, first President of the Swiss Confederation (d. 1861)
- March 23 – Sears Cook Walker, American mathematician and astronomer (d. 1853)
- March 26 – Shirali Muslimov, World's longest lived person than Jeanne Calment (d. 1973)
- April 2 – Hans Christian Andersen, Danish writer (d. 1875)
- April 8 – Hugo von Mohl, German botanist (d. 1872)
- June 9 – José Trinidad Cabañas, Honduran General, President and National Hero (d. 1871)
- June 22 – Giuseppe Mazzini Italian patriot, statesman, and writer (d. 1872)
- July 29 – Alexis de Tocqueville, French historian (d. 1859)
- August 4 – William Rowan Hamilton, Irish physicist (d. 1865)
- September 27 – George Müller, Prussian evangelist and founder of the Ashley Down orphanage in England (d. 1898)
- November 14 – Fanny Mendelssohn, German composer and pianist (d. 1847)
- November 28 – John Lloyd Stephens, American traveler, diplomat and Mayanist archaeologist (d. 1852)
- December 2 – Cicero Price, American commodore (d. 1888)
- December 22 – John Obadiah Westwood, English entomologist (d. 1893)
- December 23 – Joseph Smith, founder of the Latter Day Saint movement (d. 1844)
- January 9 – Noble Wimberly Jones, American Continental Congressman (b. 1723)
- January 18 – John Moore (archbishop of Canterbury) (b. 1730)
- January 23 – Claude Chappe, French telecommunication pioneer (b. 1763)
- February 25 – Thomas Pownall, English colonial statesman (b. 1722)
- March 4 – Jean-Baptiste Greuze, French painter (b. 1725)
- May 7 – William Petty, 2nd Earl of Shelburne, Prime Minister of the United Kingdom (b. 1737)
- May 9 – Friedrich Schiller, German playwright (b. 1759)
- May 12 – Ferdinand von Hompesch zu Bolheim, 71st Grandmaster of the Order of Malta (b. 1744)
- May 25 – William Paley, English philosopher (b. 1743)
- May 28 – Luigi Boccherini, Tuscan-born composer (b. 1743)
- June 19 – Louis-Jean-François Lagrenée, French painter (b. 1724)
- August 3 – Christopher Anstey, English writer (b. 1724)
- August 28 – Alexander Carlyle, Scottish church leader (b. 1722)
- October 5 – Charles Cornwallis, 1st Marquess Cornwallis, British general (b. 1738)
- October 21 – Horatio Nelson, British admiral (mortally wounded in battle) (b. 1758)
- December 23 – Pehr Osbeck, Swedish explorer and naturalist (b. 1723)