1826 (MDCCCXXVI) was a common year starting on Sunday of the Gregorian calendar and a common year starting on Friday of the Julian calendar, the 1826th year of the Common Era (CE) and Anno Domini (AD) designations, the 826th year of the 2nd millennium, the 26th year of the 19th century, and the 7th year of the 1820s decade. As of the start of 1826, the Gregorian calendar was 12 days ahead of the Julian calendar, which remained in localized use until 1923.
|Ab urbe condita||2579|
|Balinese saka calendar||1747–1748|
|British Regnal year||6 Geo. 4 – 7 Geo. 4|
|Chinese calendar||乙酉年 (Wood Rooster)|
4522 or 4462
— to —
丙戌年 (Fire Dog)
4523 or 4463
|- Vikram Samvat||1882–1883|
|- Shaka Samvat||1747–1748|
|- Kali Yuga||4926–4927|
|Japanese calendar||Bunsei 9|
|Julian calendar||Gregorian minus 12 days|
|Minguo calendar||86 before ROC|
|Thai solar calendar||2368–2369|
1952 or 1571 or 799
— to —
1953 or 1572 or 800
- January 15 – The French newspaper Le Figaro begins publication in Paris, initially as a weekly.
- January 30 – The Menai Suspension Bridge, built by engineer Thomas Telford, is opened between the island of Anglesey and the mainland of Wales.
- February 8 – Unitarian Bernardino Rivadavia becomes the first President of Argentina.
- February 11
- February 13 – The American Temperance Society is founded.
- February 23 – Russian Mathematician Nikolai Ivanovich Lobachevsky develops non-Euclidian geometry (independently of Janos Bolyai).
- February 24 – The Treaty of Yandabo ends the First Anglo-Burmese War; Britain gains Assam, Manipur, Rakhine and Tanintharyi.
- March 1 – Chunee the elephant is put to death in London. After arsenic and shooting fail, he is killed with a sword.
- March 10 – João VI, King of Portugal and the former Emperor of Brazil, dies after a short illness that had started six days earlier, after he had been served dinner while visiting Jerónimos Monastery. An investigative autopsy 174 years later will discover that he had been killed by arsenic poisoning. King João's son, Emperor Pedro I of Brazil, sails back to Portugal and briefly reigns as King Pedro IV, before turning over the Portuguese throne to his daughter, Maria.
- April 1 – Samuel Morey patents an internal combustion engine in the United States.
- April 10 – The Third Siege of Missolonghi ends, with the massacre of thousands of Greek defenders by the Ottoman besiegers.
- May 28 – Pedro I of Brazil abdicates as King of Portugal.
- June – Photography: Nicéphore Niépce makes a true photograph.
- June 14–15 – The Auspicious Incident: Mahmud II, sultan of Ottoman Empire, crushes the last mutiny of janissaries in Istanbul.
- June 21 – Greek War of Independence: The attempted Ottoman–Egyptian invasion of Mani begins.
- June 22 – The Pan-American Congress of Panama tries (unsuccessfully) to unify the republics of the Americas.
- July – Ludwig van Beethoven puts the finishing touches on the String Quartet in C sharp Minor, Opus 131, the jewel in the crown of his late string quartets.
- July 4 – Former U.S. Presidents Thomas Jefferson and John Adams both die on the 50th anniversary of the signing of the United States Declaration of Independence.
- July 26 – Cayetano Ripoll becomes the last person to be executed by the Spanish Inquisition at its last auto-da-fé, held in Valencia.
- August – The town of Crawford Notch, New Hampshire suffers a landslide; those killed include the Willey Family, after whom Mount Willey is named.
- August 10 – The first Cowes Regatta is held on the Isle of Wight, in the U.K.
- August 18 – Explorer Alexander Gordon Laing becomes the first European to reach Timbuktu.
- September 21 – Construction of the Rideau Canal begins in Canada.
- September – William Morgan (anti-Mason) of Batavia, New York, disappears mysteriously. It is highly likely he was murdered by freemasons.
- October 1 – The Monkland and Kirkintilloch Railway opens in Scotland.
- October 7 – The first train operates over the Granite Railway in Massachusetts.
- November 3 – The Paris Stock Exchange opens at the Palais de la Bourse.
- December 16 – Benjamin W. Edwards rides into Mexican-controlled Nacogdoches, Texas, and declares himself ruler of the Republic of Fredonia.
- December 21 – Fredonian Rebellion: American settlers in Mexican Texas make the first attempt to secede from Mexico, establishing the Republic of Fredonia, which will survive for just over a month.
- December 25
- The first railway tunnel is built en route between Liverpool and Manchester, in England.
- The British East India Company colony of the Straits Settlements is established.
- Aniline is first isolated from the destructive distillation of indigo, by Otto Unverdorben.
- Ludwig van Beethoven composes the Große Fuge.
- Mahmud II's council orders the janissaries to drill in the European manner.
- January 1 – Mikhail Loris-Melikov, Russian statesman, general (d. 1888)
- January 12 – William Chapman Ralston, American banker, financier (d. 1875)
- January 15 – Marie Pasteur, French chemist (d. 1910)
- January 24 – William Daniel, American temperance movement leader (d. 1897)
- January 26 – Louis Favre, Swiss engineer (d. 1879)
- January 27
- January 30 – Robert F. R. Lewis, American naval officer (d. 1881)
- February 3 – Walter Bagehot, English economist and journalist (d. 1877)
- February 7 – James Edward Jouett, American admiral (d. 1902)
- February 9 – John A. Logan, American soldier, political leader (d. 1886)
- February 15 – George Johnstone Stoney, Anglo-Irish physicist (d. 1911)
- February 16
- March 3 – Joseph Wharton, American industrialist (d. 1909)
- March 4
- March 24 – Matilda Joslyn Gage, American feminist (d. 1898)
- March 29 – Wilhelm Liebknecht, German journalist, politician (d. 1900)
- April 3
- April 6 – Gustave Moreau, French painter (d. 1898)
- May 3 – King Charles XV of Sweden and Norway (d. 1872)
- May 4 – Frederic Edwin Church, American painter (d. 1900)
- May 7 – Varina Davis, First Lady of the Confederate States of America (d. 1906)
- May 8 – Miguel Ângelo Lupi, Portuguese painter (d. 1883)
- May 24 – Marie Goegg-Pouchoulin, Swiss international women's rights activist, pacifist (d. 1899)
- May 26 – Richard Christopher Carrington, English astronomer (d. 1875)
- May 28 – Benjamin Gratz Brown, American politician (d. 1885)
- June 24 – George Goyder, surveyor-general of South Australia (d. 1898)
- June 26 – Warren F. Daniell, American politician (d. 1913)
- June 30 – Ozra Amander Hadley, American politician (d. 1915)
- July 4
- July 8 – Benjamin Grierson, American Civil War general (d. 1911)
- July 31 – William S. Clark, American chemist, 3rd President of the Massachusetts Agricultural College (d. 1886)
- August 7 – August Ahlqvist, Finnish professor, poet, scholar of the Finno-Ugric languages, author, and literary critic (d. 1889)
- August 11 – Andrew Jackson Davis, American spiritualist (d. 1910)
- August 21 – Karl Gegenbaur, German anatomist, professor (d. 1903)
- September 8 – Sir James Corry, 1st Baronet, British politician (d. 1891)
- September 17 – Bernhard Riemann, German mathematician (d. 1866)
- October 8 – Emily Blackwell, American physician (d. 1910)
- November 24 – Carlo Collodi, Italian writer (d. 1890)
- November 27 – Jonathan Young, United States Navy commodore (d. 1885)
- December 3 – George B. McClellan, American general, politician (d. 1885)
- December 8 - John Brown, Scottish personal servant and favourite of Queen Victoria (d. 1883)
- January 3
- January 17 – Juan Crisóstomo Arriaga, Spanish composer (b. 1806)
- January 23 – Abraham Woodhull, Patriot spy during the American Revolutionary War (b. 1750)
- February 17 – John Manners-Sutton, British politician (b. 1752)
- March 10 – King John VI of Portugal (b. 1767)
- March 29 – Johann Heinrich Voss, German poet (b. 1751)
- April 11 – Anton Walter, Austrian piano maker (b. 1752)
- April 25 – Karl Ludwig von Phull, German military leader (b. 1757)
- May 4 – Sebastián Kindelán y O'Regan, Spanish colonial governor in Cuba (b. 1757)
- May 7 – Sophie Hagman, Swedish ballerina, royal mistress (b. 1758)
- May 16
- June 3 – Nikolay Karamzin, Russian language reformer (b. 1766)
- June 5 – Carl Maria von Weber, German composer (b. 1786)
- June 7 – Joseph von Fraunhofer, German optician (b. 1787)
- July 4
- July 5
- July 8 – Luther Martin, delegate to the American Constitutional Convention (b. 1746)
- July 22 – Giuseppe Piazzi, Italian astronomer (b. 1746)
- July 25 – Sergey Muravyov-Apostol, Russian Army officer (b. 1796)
- July 26 – James Winchester, American general and politician (b. 1752)
- August 2 – George Finch, 9th Earl of Winchilsea, English cricketer (b. 1752)
- August 13 – René Laennec, French physician (b. 1781)
- August 15 – Hanne Tott, Danish circus artist, manager (b. 1771)
- August 28 – Józef Zajączek, Polish general, politician (b. 1752)
- September 7 – Robert Wright (politician), American politician (b. 1752)
- September 12 – Eliphalet Pearson, American educator (b. 1752)
- October 25 – Philippe Pinel, French physician (b. 1745)
- November 17 – Caroline Müller, Danish opera singer (b. 1755)
- November 23 – Johann Elert Bode, German astronomer (b. 1747)
- December 11 – Queen-Empress Maria Leopoldina, consort of Pedro IV of Portugal & I of Brazil (b. 1797)
- Kaushik Roy and Sourish Saha, Armed Forces and Insurgents in Modern Asia (Routledge, 2016)
- Caroline Grigson, Menagerie: The History of Exotic Animals in England (Oxford University Press, 2016)
- "Icons, a portrait of England 1820-1840". Archived from the original on September 22, 2007. Retrieved September 12, 2007.
- Penguin Pocket On This Day. Penguin Reference Library. 2006. ISBN 0-14-102715-0.
- Awdry, Christopher (1990). Encyclopaedia of British Railway Companies. Wellingborough: Patrick Stephens Ltd. ISBN 1-85260-049-7.
- "Granite Railway". Britannica Online Encyclopedia. Retrieved May 19, 2008.
- "The First Railroad in America". Catskill Archive. Granite City B.P.O.E. - Quincy Lodge No. 943. 1924. Retrieved May 19, 2008.
- Jacques Sirat, Braquenié: French Textiles and Interiors Since 1823 (Antique Collectors Club Limited, 1998) p16
- "The Bourse", in Frank Leslie's New Family Magazine (July 1858) p42
- Hughes, Derrick (1986). Bishop Sahib: A Life of Reginald Heber. Worthing, UK: Churchman Publishing. pp. 178–180. ISBN 978-1-85093-043-3.
- H. K. Riikonen. "Ahlqvist, August (1826-1889)" (in Finnish). kansallisbiografia. Retrieved July 6, 2021.
- "BBC - History - John Adams". www.bbc.co.uk. Retrieved March 29, 2022.