1866
Events
January
- January 1
- * Fisk University, a historically black university, is established in Nashville, Tennessee.
- * The last issue of the abolitionist magazine The Liberator is published.
- January 6 – Ottoman troops clash with supporters of Maronite leader Youssef Bey Karam, at St. Doumit in Lebanon; the Ottomans are defeated.
- January 12
- * The Royal Aeronautical Society is formed as The Aeronautical Society of Great Britain in London, the world's oldest such society.
- * British auxiliary steamer sinks in a storm in the Bay of Biscay, on passage from the Thames to Australia, with the loss of 244 people, and only 19 survivors.
- January 18 – Wesley College, Melbourne, is established.
- January 26 – Volcanic eruption in the Santorini caldera begins.
February
March
April
May
File:ShieldNickel.jpeg|thumb|260px|right| May 16: U.S. nickel coin approved.
- May 10 - London bank Overend, Gurney and Company collapses, precipitating Panic of 1866.
- May 16 - The United States Congress approves the minting of a nickel 5-cent coin, eliminating its predecessor, the half dime.
- May 24 - Battle of Tuyutí: 32,000 soldiers of the Triple Alliance defeat 24,000 Paraguayan soldiers few miles north of the Paraná, Argentina, in the Paraguayan War, with 16,000 casualties.
- May 26 - First production of the comic opera Cox and Box by F. C. Burnand and Arthur Sullivan at Moray Lodge, Kensington
- May 30 - Bedrich Smetana's comic opera The Bartered Bride premiered in Prague.
June
July
File:Atlantic cable Map.jpg|thumb|July 27: Atlantic Cable completed
August
October
November
December
Date unknown
Births
January–March
- January 10 – Hermanus Johannes Lovink, Dutch agriculturalist and politician
- January 13
- * George Gurdjieff, Russian spiritual teacher
- * Vasily Kalinnikov, Russian composer
- January 15
- * Nathan Söderblom, Swedish archbishop, recipient of the Nobel Peace Prize
- * Horatio Dresser, American New Thought religious leader and writer
- January 16 – Percy Pilcher, English inventor and pioneer aviator
- January 19 – Harry Davenport, American actor
- January 29
- * Romain Rolland, French writer, Nobel Prize laureate
- * Frank Tudor, Australian politician
- February 1 – Agda Meyerson, Swedish nurse and healthcare profession activist
- February 2 – Enrique Simonet, Spanish painter
- February 9 – George Ade, American writer, newspaper columnist and playwright
- February 18 – Janko Vukotić, Montenegrin general
- February 26 – Herbert Henry Dow, Canadian chemical industrialist
- March 5 – Arthur Leopold Busch, English-born American submarine pioneer
- March 7 – Hans Fruhstorfer, German lepidopterist
- March 13 – Friedrich Boedicker, German admiral
- March 15 – Matthew Charlton, Australian politician
- March 19 – Emilio De Bono, Italian general and fascist activist
- March 21
- * James Harbord, American general
- * Wakatsuki Reijirō, 25th and 28th Prime Minister of Japan
April–June
- April 1 – Ferruccio Busoni, Italian pianist and composer
- April 3 – J. B. M. Hertzog, Boer General and 3rd Prime Minister of South Africa
- April 8 – Alfred Allen, American actor
- April 13 – Butch Cassidy, American outlaw
- April 14 – Anne Sullivan, American tutor of Helen Keller
- April 17 – Ernest Starling, English physiologist
- April 18 – Yamaya Tanin, Japanese admiral
- April 21 – Josefa Toledo de Aguerri, Nicaraguan pioneer educator
- April 22 – Hans von Seeckt, German general
- April 24 – Ishii Kikujirō, Japanese diplomat
- May 10 – Richard H. Jackson, American four-star admiral
- May 17 – Erik Satie, French composer
- May 22 – Charles F. Haanel, American New Thought author and businessman
- June 4 – Miina Sillanpää, Finnish politician
- June 26
- * George Herbert, 5th Earl of Carnarvon, English financier of Egyptian excavations
- * Josef Swickard, German actor
July–September
- July 6 – Charles Mangin, French general
- July 9 – Macklyn Arbuckle, American actor
- July 13 – La Goulue, French dancer
- July 25 – Frederick Blackman, English plant physiologist
- July 27 – António José de Almeida, 6th President of Portugal and 64th Prime Minister of Portugal
- July 28 – Beatrix Potter, English children's author
- August 2 – Adrien de Gerlache, Belgian naval officer and explorer
- August 4 – Gheorghe Mărdărescu, Romanian general and politician
- August 6 – Chief Thunderbird, Native American actor
- August 8 – Matthew Henson, African-American explorer
- August 12 – Jacinto Benavente, Spanish writer, Nobel Prize laureate
- August 14 – Dmitry Merezhkovsky, Russian novelist, poet and religious thinker
- September 1
- September 7 – Tristan Bernard, French writer
- September 10 – Jeppe Aakjær, Danish poet and novelist
- September 16 – Joe Vila, American sportswriter
- September 21
- * Charles Nicolle, French bacteriologist, recipient of the Nobel Prize in Physiology or Medicine
- * H. G. Wells, English writer
- September 22 – Witmer Stone, American ornithologist and botanist
- September 27 – Eurosia Fabris, Italian Catholic Blessed
- September 25 – Thomas Hunt Morgan, American geneticist, recipient of the Nobel Prize in Physiology or Medicine
October–December
- October 6
- * Reginald Fessenden, Canadian inventor
- * Nina Bang, Danish politician
- October 12 – Ramsay MacDonald, Scottish Prime Minister of the United Kingdom
- October 29
- * Antonio Luna, Filipino general
- * Dmitri Parsky, Russian general
- November 3 – Paul Lincke, German composer
- November 11 – Martha Annie Whiteley, English chemist and mathematician
- November 12 – Sun Yat-sen, Chinese revolutionary
- November 16 – Cornelia Sorabji, Indian-born lawyer
- November 28
- * Sy Sanborn, American sportswriter
- * David Warfield, American stage actor
- November 30
- * Robert Broom, Scottish paleontologist
- * Andrey Lyapchev, 22nd Prime Minister of Bulgaria
- December 2 – Constantin Cristescu, Romanian general
- December 11 – Ada Baker, Australian soprano, singing teacher and vaudeville star
- December 12 – Alfred Werner, German chemist, Nobel Prize laureate
- December 16 – Wassily Kandinsky, Russian-born painter
- December 17 – Kazys Grinius, 5th Prime Minister of Lithuania
- December 29 – Marie Cahill, American singer and actress
Date unknown
Deaths
January–June
- January – Thomas Baldwin Marsh, American religious leader
- January 16 – Phineas Quimby, American physician
- January 19 – Harriet Ludlow Clarke, British artist
- January 23 – Thomas Love Peacock, English satirist
- January 31 – Friedrich Rückert, German poet, translator and professor of Oriental languages
- February 25 – Sarah Ann Gill, Barbadian national heroine
- March 4 – Alexander Campbell, Irish/U.S. founder of the Disciples of Christ
- March 6 – William Whewell, English scientist, philosopher and historian of science
- March 9 – Jakob Joseph Matthys, Swiss Catholic priest
- March 20 – Rikard Nordraak, Norwegian composer
- March 21 – Nadezhda Durova, first female Russian military officer
- March 24 – Maria Amalia of Naples and Sicily, Queen of France
- March 28 – Solomon Foot, American politician
- March 29 – John Keble, British churchman
- April 1 – Elizabeth Jesser Reid, English social reformer, founder of Bedford College
- April 4 – William Dick, founder of Edinburgh Veterinary College
- April 5 – Thomas Hodgkin, British physician
- April 7 – Johann Sedlatzek, German flautist
- April 12 – Peter Hesketh-Fleetwood, English Member of Parliament and developer
- May 13 – Nikolai Brashman, Russian mathematician of Czech origin
- May 29 – Winfield Scott, American general and presidential candidate
- June 7 – Chief Sealth, Native American for whom Seattle is named
- June 17 – Lewis Cass, American military officer, politician, and statesman
July–December
- July 20 – Bernhard Riemann, German mathematician
- July 25 – Floride Calhoun, Second Lady of the United States
- July 29 – Madame Clicquot Ponsardin, French champagne producer
- August 1 – John Ross, long-serving principal chief of the Cherokee Nation, of natural causes, in Washington D. C..
- August 6 – Christian Eric Fahlcrantz, Swedish writer
- August 20 – Maria De Mattias, Italian Catholic saint
- August 29 – Tokugawa Iemochi, 14th shōgun of the Tokugawa shogunate of Japan
- September 4 – Theresa Pulszky, European author
- September 30 – Per Gustaf Svinhufvud af Qvalstad, Swedo-Finnish treasurer of Tavastia province, manor host, and paternal grandfather of President P. E. Svinhufvud
- October 13 – Celadon Leeds Daboll, American merchant and inventor
- October 18 – Manuel Bulnes, Chilean general and politician, President of Chile
- November 11 – Agustín Jerónimo de Iturbide y Huarte, Prince Imperial of Mexico
- November 14 – King Miguel I of Portugal
- November 26 – Jean-Jacques Willmar, Luxembourg politician
- December 1 – George Everest, Welsh geodesist
- December 21 – William J. Fetterman, United States Army officer
- December 21 – Mercedes Marín del Solar, Chilean poet, reform educator
- December 25 – Hayrullah Efendi, Ottoman physician, historian, and official
Date unknown