January 1 – Sailing through the Sandwich Islands, Otto von Kotzebue discovers New Year Island.
January 19 – An army of 5,423 soldiers, led by General José de San Martín, starts crossing the Andes from Argentina to liberate Chile and then Peru.
January 20 – Ram Mohan Roy and David Hare found Hindu College, Calcutta, offering instructions in Western languages and subjects.
February 12 – Battle of Chacabuco: The Argentine/Chilean patriotic army defeats the Spanish.
President James Madison vetoes John C. Calhoun's Bonus Bill.
U.S. Congress passes law to split the Mississippi Territory, after Mississippi drafts a constitution, creating the Alabama Territory effective in August.
March 4 – James Monroe is sworn in as President of the United States.
March 21 – The flag of the Pernambucan Revolt is publicly blessed by the dean of Recife cathedral, Brazil.
April – An earthquake strikes Palermo, Sicily.
April 3 – Princess Caraboo appears in Almondsbury in Gloucestershire, England.
April 15 – The American School for the Deaf opens in Hartford, Connecticut.
April 29 – The Rush–Bagot Treaty is signed.
May – The General Convention of the Episcopal Church founds the General Theological Seminary while meeting in New York City.
June 12 – German inventor Karl Drais drives his dandy horse ("Draisine" or Laufmaschine), the earliest form of bicycle, in Mannheim.
June 25 – A large riot breaks out in Copenhagen Prison; the army is sent to quell it.
July 4 – At Rome, New York, construction on the Erie Canal begins.
c. July – Tradesman Jeffery Sedwards establishes the Skibbereen Abstinence Society in Ireland, considered the first organisation devoted to teetotalism in Europe.
August 15 – By act of the U.S. Congress (March 3), the Alabama Territory is created by splitting the Mississippi Territory in half, on the day the Mississippi constitution is drafted, four months before Mississippi became a State of the United States.
August 22 – The town of Araraquara, Brazil is founded.
August 23 – An earthquake near the site of the ancient Greek city of Helike results in 65 deaths.
September 11 – The beginning of the Great Rebellion of 1817-18 in Sri Lanka
October 17 – Frigate HMS Trincomalee is launched in Bombay for the British Royal Navy; she will still be afloat two centuries later.
October 31 – Emperor Ninkō accedes to the throne of Japan.
November 5 – Third Anglo-Maratha War breaks out with the Battle of Khadki.
November 20 – The first Seminole War begins in Florida.
November 22 – Frédéric Cailliaud discovers the old Roman emerald mines at Sikait, Egypt.
December 10 – Mississippi is admitted as the 20th U.S. state, formerly the Mississippi Territory.
First cholera pandemic (1817–24) originates in Bengal, reaching Calcutta by September.
A typhus epidemic occurs in Edinburgh and Glasgow.
King Ferdinand VII of Spain, by royal decree, makes the production and sale of tobacco a legal endeavor in Cuba, thus sparking the birth of the Cuban cigar industry.
January 8 – Sir Theophilus Shepstone, British-born South African statesman (d. 1893)
February 18 – Lewis Armistead, Confederate general (d. 1863)
February 19 – King William III of the Netherlands (d. 1890)
February 22 – Carl Wilhelm Borchardt, German mathematician (d. 1880)
February 24 – Auguste-Alexandre Ducrot, French general (d. 1882)
March 6 – Princess Clémentine of Orléans, daughter of King Louis Philippe I of France and mother of Tsar Ferdinand I of Bulgaria (d. 1907)
March 22 – Braxton Bragg, American Confederate general (d. 1876)
April 1 – Nissen Shonin, Japanese Buddhist Priest Honmon Butsuryū-shū, Kyoto city (d. 1890)
April 15 – Benjamin Jowett, Master of Balliol College, Oxford (d. 1893)
April 24 – Jean Charles Galissard de Marignac, Swiss chemist (d. 1894)
May 15 – Debendranath Tagore, Indian philosopher (d. 1905)
May 19 – Theodor August Heintzman, Canadian piano manufacturer (d. 1899)
June 30 – Joseph Dalton Hooker, English botanist (d. 1911)
July 6 — Albert von Kölliker, Swiss biologist and zoologist (d. 1905)
July 12 – Henry David Thoreau, American philosopher (d. 1862)
July 15 – John Fowler, British civil engineer (d. 1898)
July 24 – Adolphe, Grand Duke of Luxembourg (d. 1905)
July 29 – Ivan Aivazovsky, Armenian-Russian painter (d. 1900)
August 3 – Archduke Albrecht, Duke of Teschen, Austrian general (d. 1895)
August 4 – Frederick Theodore Frelinghuysen, 29th United States Secretary of State (d. 1885)
August 14 – Alexander H. Bailey, American politician (d. 1874)
August 24 – Aleksey Konstantinovich Tolstoy, Russian writer (d. 1875)
September 6 – Helga de la Brache, Swedish con artist (d. 1885)
September 14 – Theodor Storm, German writer (d. 1888)
October 10 – Christophorus Buys Ballot, Dutch chemist and meteorologist (d. 1890)
October 17 – Sir Syed Ahmad Khan (Bahadaur) Founder of the Two Nation Theory for a future Pakistan (d. 1898)
November 3 – Leonard Jerome, American entrepreneur and grandfather of Sir Winston Churchill (d. 1891)
November 12 – Bahá'u'lláh, Persian founder of the Bahá'í Faith (d. 1892)
November 17 – Benjamin Champney, American painter (d. 1907)
November 30 – Theodor Mommsen, German writer, Nobel Prize laureate (d. 1903)
December 10 – Alexander Wood (physician), inventor of the first true hypodermic syringe (d. 1884)
December 23 – Warren Felt Evans, American writer (d. 1889)
Sophia Wilkens, Swedish social reformer and pioneer in the education of the intellectually disabled.
January 1 – Martin Heinrich Klaproth, German chemist who discovered uranium (1789), zirconium (1789), and cerium (1803) (b. 1743)
January 11 – Timothy Dwight IV, American educator and theologian (b. 1752)
January 11 – Margherita Dalmet, Venetian dogaressa (b. 1739)
January 12 – Juan Andrés, Spanish Jesuit (b. 1740)
January 16 – Alexander J. Dallas, American statesman and financier (b. 1759)
February 8 – Francis Horner, Scottish politician and economist (b. 1778)
March 8 – Anna Maria Lenngren, Swedish writer (b. 1754)
April 2 – Johann Heinrich Jung, German writer (b. 1740)
April 4 – André Masséna, French marshal (b. 1758)
April 12 – Charles Messier, French astronomer (b. 1730)
April 20 – Infante Antonio Pascual of Spain, Spanish prince (b. 1755)
June 2 – Clotilde Tambroni, Italian philologist and linguist (b. 1758)
June 4 – George Farragut, American naval officer (b. 1755)
June 9 – Théroigne de Méricourt, French revolutionary (b. 1762)
June 18 – Leonard Neale, American Catholic bishop (b. 1746)
June 20 – Marie-Gabriel-Florent-Auguste de Choiseul-Gouffier, French diplomat (b. 1752)
June 24 – Thomas McKean, American lawyer and signer of the Declaration of Independence (b. 1734)
June 30 – Abraham Gottlob Werner, German geologist (b. 1750)
July 14 – Anne Louise Germaine de Staël, French writer (b. 1766)
July 18 – Jane Austen, English novelist (b. 1775)
July 19 – John Palmer, Bath architect (b. c. 1738)
July 24 – Karađorđe Petrović, Serb leader of the First Serbian Uprising against the Ottoman Empire, and the founder of the Serbian Karađorđević dynasty (b. 1768)
August 10 – Leopold III, Duke of Anhalt-Dessau (b. 1740)
October 11 – Gertrudis Bocanegra, Mexican national heroine (b. 1765)
October 13 – Julius Caesar Ibbetson, English artist (b. 1759)
October 15 – Tadeusz Kościuszko, exiled Polish general and nationalist (b. 1746)
October 16 – Manuel Piar, Venezuelan military leader (b. 1774)
November 6 – Princess Charlotte of Wales, English-born princess (b. 1796)
November 7 – Jean-André Deluc, Swiss geologist (b. 1727)
November 11 – Francisco Javier Mina, Spanish military leader (b. 1789) (executed)
November 14 – Policarpa Salavarrieta, Colombian spy and revolutionary who worked for the Independence of Colombia (b. 1795)
November 30 – Jean-Baptiste-Melchior Hertel de Rouville, Canadian politician (b. 1748)
December 7 – William Bligh, British admiral (b. 1754)
December 12 – Emperor Tekle Giyorgis I of Ethiopia, (b. c. 1751)
Usman dan Fodio, founder of Sokoto caliphate, (b. 1754)
1817 (MDCCCXVII) was a common year starting on Wednesday (dominical letter E) of the Gregorian calendar and a common year starting on Monday (dominical letter G) of the Julian calendar, the 1817th year of the Common Era (CE) and Anno Domini (AD) designations, the 817th year of the 2nd millennium, the 17th year of the 19th century, and the 8th year of the 1810s decade. As of the start of 1817, the Gregorian calendar was 12 days ahead of the Julian calendar, which remained in localized use until 1923.