1805

January–March

• January 11 – The 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–June

• 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
  • The first Trooping the Colour ceremony is held at the Horse Guards Parade in London.
  • Detroit burns to the ground; most of the city is destroyed.
• 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–September

• July 9 – Muhammad Ali Pasha founds his dynasty in Egypt.
• July 26 – An earthquake kills 5,573 people in Molise and Campania, Italy.
• August 12 – Lewis and Clark Expedition: U.S. Army Captain Meriwether Lewis becomes the first white person to reach the Continental Divide, that marks the division between the east and west sections of the North American continent, crossing at Lemhi Pass.^[1]
• August 29 – Emperor Franz I of Austria and his council of ministers vote in favor of going to war with France.^[2]
• August 31 – British Army General David Baird departs from Cork, leading an expedition to capture the Cape of Good Hope. Their ship arrives on January 4.^[3]
• September 21 – King Ferdinand of Naples signs a treaty in Paris, agreeing to keep Naples neutral during the war between France and the allied powers.^[4]
• September 29 – Admiral Nelson of the Royal Navy takes command of the fleet off of the coast of Cadiz, in order to counteract the navies of France and Spain.^[5]

October–December

• October 14 – Napoleonic Wars – War of the Third Coalition – Ulm Campaign – Battle of Elchingen: An Austrian corps under Johann von Riesch is defeated by Marshal Ney, near Elchingen, Bavaria.
• October 16–19 – War of the Third Coalition – Ulm Campaign – Battle of Ulm: Austrian General Mack von Leiberich is forced to surrender his entire army to Napoleon, after being surrounded.
• October 21 – Napoleonic Wars – War of the Third Coalition – Battle of Trafalgar: The British fleet, led by Admiral Horatio Nelson, defeats a combined French and Spanish fleet off the coast of Spain; however, Admiral Nelson is fatally shot.
• October 31 – Sweden, led by King Gustav IV Adolf, declares war on France.^[6]
• 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: Battle of Austerlitz

• 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.
• December 31 – The French Republican Calendar (which featured a 10-day week until 1802) is used for the last time, 8 days after being annulled by Napoleon, with the final official date being "9 Nivôse in Year XIV of the Revolution".^[7]

Date unknown

• King Anouvong becomes ruler of Vientiane.
• The Horse Patrol, a mounted law enforcement force, is founded in London, England.
• James Squire becomes the first brewer in Australia to cultivate hops.
• The Old Man of the Mountain, a natural rock formation in the U.S. state of New Hampshire, is first mentioned by two workmen, Francis Whitcomb and Luke Brooks.
• Napoleon orders his soldiers to be vaccinated.

January–June

Hans Christian Andersen

• January 8 – Orson Hyde, American religious leader (d. 1878)
• January 27 – Samuel Palmer, English artist (d. 1881)
• February 13 – Peter Gustav Lejeune Dirichlet, German mathematician (d. 1859)
• 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, 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)
• April 22 – Benito de Soto, Galician pirate (d. 1830)
• 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–December

Fanny Mendelssohn

Joseph Smith

Jeanne Deroin

• July 5 – Robert FitzRoy, English meteorologist, captain and politician (d. 1865)
• July 29 – Alexis de Tocqueville, French historian (d. 1859)
• July 30 – Rudolf Wagner, German anatomist, pathologist (d. 1864)
• August 4 – William Rowan Hamilton, Irish physicist (d. 1865)
• September 19 – John Stevens Cabot Abbott, American historian, pastor, and pedagogical writer (d. 1877)
• September 27 – George Müller, Prussian evangelist, founder of the Ashley Down orphanage in England (d. 1898)
• November 14 – Fanny Mendelssohn, German composer, 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 10 – William Lloyd Garrison, American abolitionist (d. 1879)
• December 12 – Henry Wells, founder of Wells Fargo (d. 1878)
• December 22 – John Obadiah Westwood, English entomologist (d. 1893)
• December 23 – Joseph Smith, founder of The Church of Jesus Christ of Latter Day Saints Church and Latter Day Saint movement (d. 1844)
• December 31 – Jeanne Deroin, French socialist, feminist (d. 1894)
• date unknown
  • Maiden of Ludmir, Jewish religious leader (d. 1888)

January–June

Friedrich Schiller

Lord Nelson

• January 9 – Noble Wimberly Jones, American Continental Congressman (b. 1723)
• January 17 – Paschen von Cossel, German lawyer (b. 1714)
• January 18 – John Moore (archbishop of Canterbury) (b. 1730)
• January 23 – Claude Chappe, French telecommunication pioneer (b. 1763)
• February 20 – Justus Claproth, German jurist, inventor of the de-inking process of recycled paper (b. 1728)
• 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 25 – Anna Maria Rückerschöld, Swedish author (d. 1725)
• May 28 – Luigi Boccherini, Tuscan-born composer (b. 1743)
• June 19 – Louis-Jean-François Lagrenée, French painter (b. 1724)

July–December

Eleonore Prochaska

• 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 5 – Eleonore Prochaska, German heroine soldier (b. 1785)
• October 21 – Horatio Nelson, British admiral (mortally wounded in battle) (b. 1758)
• December 16 – Saverio Cassar, Gozitan priest, rebel leader (b. 1746)
• December 23 – Pehr Osbeck, Swedish explorer, naturalist (b. 1723)
• December 23 – Geneviève Thiroux d'Arconville, French novelist, translator and chemist (b. 1720)
• date unknown
  • Rafaela Herrera, Nicaraguan heroine (b. 1742)
  • Bety of Betsimisaraka, queen regnant (b. 1735)