|Covid-19|January 8 – An unsuccessful slave revolt is led by Charles Deslondes in St. Charles and St. James, Louisiana.
January 22 – The Casas Revolt begins in San Antonio, Texas.
February 5 – British Regency: George, Prince of Wales becomes Prince Regent because of the perceived insanity of his father, King George III of the United Kingdom.
February 19 – Peninsular War: Battle of the Gebora – An outnumbered French force under Édouard Mortier routs and nearly destroys the Spanish near Badajoz in Spain.
March 1 – Citadel Massacre in Cairo: Egyptian ruler Muhammad Ali kills the last Mamluk leaders.
March 5 – Peninsular War: Battle of Barrosa, an unsuccessful French attack on a larger Anglo-Portuguese-Spanish force attempting to lift the Siege of Cádiz in Spain.
March 13 – Battle of Lissa: The British fleet defeats the French.
March 22 – The Commissioners' Plan for Manhattan is presented.
March 25 – Great Comet discovered by Honoré Flaugergues.
March 27 – Battle of Anholt: The British Navy defeats Denmark.
March 28 – Henri Christophe is proclaimed King Henri I, turning the northern State of Haiti into the Kingdom of Haiti.
April 5–6 – Revolutionary riots occur in Buenos Aires.
May 14 – Paraguay declares independence from the Spanish Empire (recognised May 15).
May 16 – Peninsular War Battle of Albuera: Spain, Portugal and Great Britain defeat the French.
May 18 – The Battle of Las Piedras is fought near Las Piedras, Banda Oriental, resulting in the first victory for the independentists of Uruguay.
June 9 – The Great Podil fire breaks out in Kiev, Ukraine.
June 15 – The Klågerup riots in Sweden.
July 5 – Venezuela declares its Independence from the Spanish Empire.
July 9 – British explorer David Thompson posts a notice at the confluence of the Columbia and Snake Rivers (in modern-day Washington (state)) claiming the area for the United Kingdom.
July 11 – The Russian Empire removes Anton II, Catholicos-Patriarch of All Georgia, from his office, placing a Russian-appointed bishop at the head of the Georgian church.
Italian scientist Amedeo Avogadro publishes his memoire about the molecular content of gases.
David Thompson reaches the mouth of the Columbia River, finding Fort Astoria under construction.
July 30 — Mexican War of Independence: Priest and military leader Miguel Hidalgo y Costilla is executed as a rebel by the Spanish government of New Spain.
August 3 – First ascent of Jungfrau, third highest summit in the Bernese Alps,
September – Nathan of Breslov leads the first annual Rosh Hashana kibbutz (pilgrimage) of Breslov Hasidim to the grave of Rabbi Nachman of Breslov in Uman, Ukraine.
October 11 – Inventor John Stevens' boat, the Juliana, begins operation as the first steam-powered ferry service, between New York City and Hoboken, New Jersey.
October 23 – José Gervasio Artigas and 16.000 orientales leave the Banda Oriental del Uruguay to go into exile.
October 26 – The Argentine Government declares freedom of expression for the press.
November – Luddite uprisings begin in northern England and the Midlands.
November 7 – Battle of Tippecanoe: American troops led by William Henry Harrison defeat the Native American spiritual leader Tenskwatawa, also known as The Prophet (Chief Tecumseh's brother).
November 17 – José Miguel Carrera, Chilean founding father, is sworn in as President of the executive Junta of the government of Chile.
December 2 – Reverend Samuel Marsden sends the first commercial shipment of wool from New South Wales to England.
December 16 – The New Madrid earthquake in the Mississippi Valley near New Madrid reverses the course of the river for a while. Other earthquakes along the fault occur on January 23, 1812 and February 7, 1812.
December 21 – First Constitution of Republic of Venezuela after declares its independence from Spain.
The Red River Colony is founded in Manitoba, Canada.
January 6 – Charles Sumner, American senator and civil rights activist (d. 1874)
January 9 – Gilbert Abbott à Beckett, English writer (d. 1856)
February 1 – Arthur Hallam, English poet (d. 1833)
February 3 – Horace Greeley, American journalist, editor, and publisher (d. 1872)
February 6 – Henry George Liddell, English clergyman (d. 1898)
February 13 – François Achille Bazaine, French general (d. 1888)
February 15 – Domingo Faustino Sarmiento, Argentinian politician, writer and father of education (d. 1888)
Napoleon II of France (d. 1832)
Alfred Domett, 4th Premier of New Zealand (d. 1887)
March 21 – Nathaniel Woodard, English educationalist (d. 1891)
March 30 or March 31 – Robert Bunsen, German chemist and inventor (d. 1899)
Chang and Eng Bunker, Siamese twins and sideshow performers (d. 1874)
Jean-Jacques Challet-Venel, member of the Swiss Federal Council (d. 1893)
June 3 – Henry James, Sr., American theologian (d. 1882)
June 14 – Harriet Beecher Stowe, American author (d. 1896)
June 17 – Jón Sigurðsson, the leader of the 19th century Icelandic independence movement. (d. 1879)
June 24 – John Archibald Campbell, Associate Justice of the Supreme Court of the United States (d. 1889)
Isaac A. Van Amburgh, American animal trainer (d. 1865)
William Robert Grove, Welsh chemist and Inventor (d. 1896)
July 13 – George Gilbert Scott, British architect (d. 1878)
July 18 – William Makepeace Thackeray, British novelist (d. 1863)
August 11 – Judah P. Benjamin, Cabinet officer of the Confederate States (d. 1884)
August 31 – Théophile Gautier, French writer (d. 1872)
September 13 – Emmanuel Félix de Wimpffen, French general (d. 1884)
September 19 – Orson Pratt, American religious leader (d. 1881)
October 22 – Franz Liszt, Hungarian composer and pianist (d. 1886)
Évariste Galois, French mathematician (d. 1832)
C. F. W. Walther, German-American theologian (d. 1887)
October 27 – Stevens Thomson Mason, first governor of Michigan (d. 1843)
November 21 – Ludwig Preiss, Botanical collector (d. 1883)
November 24 – Ulrich Ochsenbein, Swiss Federal Councilor (d. 1890)
November 26 – Zeng Guofan, Chinese official and military leader (d. 1872)
November 28 – King Maximilian II of Bavaria (d. 1864)
December 5 – Justus Carl Hasskarl, German explorer and botanist (d. 1894)
December 21 – Archibald Campbell Tait, Archbishop of Canterbury (d. 1882)
Mohammad Afzal Khan, Emir of Kabul, Emir of Kandahar (d. 1867)
January 10 – Marie-Joseph Chénier, French poet (b. 1764)
February 26 – Mateo de Toro Zambrano, 1st Count of La Conquista, Governor of Chile (b. 1727)
March 14 – Augustus FitzRoy, 3rd Duke of Grafton, Prime Minister of the United Kingdom (b. 1735)
April 7 – Garsevan Chavchavadze, Georgian diplomat and politician (b. 1757)
May 4 – Nikolay Kamensky, Russian general (b. 1776)
May 28 – Henry Dundas, 1st Viscount Melville, British minister (b. 1742)
June 26 – Ignacio Allende, captain of the Spanish Army in Mexico
July 30 – Miguel Hidalgo y Costilla, Mexican revolutionary (b. 1753)
August – William Williams, signer of the United States Declaration of Independence (b. 1731)
August 31 – Louis Antoine de Bougainville, French navigator and military commander (b. 1729)
September – Ulrich Jasper Seetzen, explorer (b. 1767)
September 8 – Peter Simon Pallas, German zoologist (b. 1741)
September 14 - Johanna Löfblad, Swedish actor and singer (b. 1733)
October 11 – Johann Conrad Ammann, Swiss physician and naturalist (b. 1724)
October 15 – Eva Merthen, Finnish political activist (b. 1723)
November 21 – Heinrich von Kleist, German writer (suicide) (b. 1777)
November 27 – Andrew Meikle, Scottish engineer (b. 1719)
1811 (MDCCCXI) was a common year starting on Tuesday (dominical letter F) of the Gregorian calendar and a common year starting on Sunday (dominical letter A) of the Julian calendar, the 1811th year of the Common Era (CE) and Anno Domini (AD) designations, the 811th year of the 2nd millennium, the 11th year of the 19th century, and the 2nd year of the 1810s decade. As of the start of 1811, the Gregorian calendar was 12 days ahead of the Julian calendar, which remained in localized use until 1923.