1802 1803 1804 - 1805 - 1806 1807 1808
| Decades: |
1770s 1780s 1790s - 1800s - 1810s 1820s 1830s
| Centuries: |
18th century - 19th century - 20th century
- January 11 - Michigan Territory is created.
- February 15 - Harmony Society officially formed
- March 1 - Justice Samuel Chase acquitted of impeachment charges by the U.S. Senate
- April 27 - United States Marines and Berbers attack the Tripolitan city of Derna (The "shores of Tripoli").
- May 26 - In Milan's cathedral, Napoleon I of France is crowned King of Italy.
- June 1 - Luigi Boccherini was buried in Italy after being found found dead on May 28.
- June - War ends between Tripoli and the United States of America.
- June 4 - The first Trooping the Colour ceremony at the Horse Guards Parade in London
- June 13 - Lewis and Clark Expedition: 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.
- 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. Admiral Nelson is fatally shot
- November 16 - Battle at Schungrabern - Russian army stops the French
- December 2 - Napoleonic Wars: Battle of Austerlitz - French troops under Napoleon decisively defeat a joint Russo-Austrian force.
- December 26 – Peace of Pressburg between France and Austria
- Sweden declares war on France
- Horse Patrol, mounted law enforcement force, founded in London, England
- Napoleon annuls the ten-day week of the French Revolutionary Calendar. He also orders his soldiers to be vaccinated
- March 3 - Jonas Furrer, Swiss politician and first President of the Swiss Confederation (d. 1861)
- April 2 - Hans Christian Andersen, writer (d. 1875)
- August 29 - Frederick Maurice, English theologian (d. 1872)
- November 14 - Fanny Mendelssohn, composer and pianist
- December 22 - John Obadiah Westwood, British entomologist
- December 23 - Joseph Smith, Jr., religious leader, founded Mormonism
- January 23 - Claude Chappe, telecommunication pioneer (semaphores)
- May 9 - Friedrich Schiller, German playwright.
- May 25 - William Paley, philosopher
- May 28 - Luigi Boccherini, Italian classical music performer
- October 21 - Horatio Nelson, British admiral.af:1805
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