|Centuries:||18th century – 19th century – 20th century|
|Decades:||1830s 1840s 1850s – 1860s – 1870s 1880s 1890s|
|Years:||1864 1865 1866 – 1867 – 1868 1869 1870|
- January 14 – Jean Auguste Ingres, French painter (b. 1780)
- January 30 – Emperor Komei of Japan (b. 1831)
- May 12 – Friedrich William Eduard Gerhard, German archaeologist (b. 1795)
- June 19 – Maximilian, Emperor of Mexico (executed) (b. 1832)
- August 25 – Michael Faraday, English chemist and physicist (b. 1791)
- August 31 – Charles Baudelaire, French writer (b. 1821)
- September 10 – Simon Sechter, Austrian music teacher (b. 1788)
- Alexander Bryan Johnson, American philosopher (b. 1786)
- January 1 – The John A. Roebling Suspension Bridge opens between Cincinnati, Ohio and Covington, Kentucky, becoming the longest suspension bridge in the world
- January 8 – African-American men granted the right to vote in the District of Columbia
- January 11 – Benito Juárez becomes Mexican president again
- January 30 – Emperor Komei of Japan dies. Crown Prince Mutsuhito is expected to become the next Emperor of Japan.
- January 31 – Maronite nationalist leader Karam leaves Lebanon on board of a French ship for Algeria
- February 3 – Shogun Tokugawa Yoshinobu abdicates, and the late Emperor Komei's son, Prince Mutshuhito becomes Emperor Meiji of Japan. End of the Late Tokugawa shogunate.
- February 17 – The first ship passes through the Suez Canal
- March 1 – Nebraska is admitted as the 37th U.S. state.
- March 16 – First publication of an article by Joseph Lister outlining the discovery of antiseptic surgery, in The Lancet.
- March 29 – The British North America Act receives royal assent, forming the Dominion of Canada in an event known as Confederation. This unites the Province of Canada, Quebec, Ontario, New Brunswick, and Nova Scotia as of July 1. Ottawa becomes the capital, and John A. Macdonald becomes the Dominion's first prime minister.
- March 30 – Alaska is purchased for $7.2 million from Alexander II of Russia, about 2 cent/acre ($4.19/km2), by United States Secretary of State William H. Seward. The news media call this "Seward's Folly."
- April 1 – Strait Settlement of Singapore, formerly ruled from Calcutta, becomes a Crown Colony under the jurisdiction of the Colonial Office in London
- May 29 – Austro-Hungarian agreement called Ausgleich ("the Compromise") is born through Act 12, which established the Austro-Hungarian Monarchy; on June 8 Emperor Francis Joseph was crowned King of Hungary
- June 19 – Firing squad executes Emperor Maximilian of Mexico
- July 1 – Canada Day, recognizing the creation of Canada by the British North America Act.
- July 17 – In Boston, Massachusetts, the Harvard School of Dental Medicine is established as the first dental school in the United States.
- July 21 – Missionary Thomas Baker killed and eaten in Viti Levu, Fiji
- September 2 – Mutsuhito, the Meiji Emperor of Japan marries Ichijo Masako. The Empress consort is thereafter known as Lady Haruko.
- September 30 – The United States takes control of Midway Island.
- October 21 – 'Manifest Destiny': Medicine Lodge Treaty – Near Medicine Lodge Creek, Kansas a landmark treaty is signed by southern Great Plains Indian leaders. The treaty requires Native American Plains tribes to relocate a reservation in western Oklahoma.
- October 27 – Giuseppe Garibaldi's troops march into Rome
- December 2 – In a New York City theater, British writer Charles Dickens gives his first public reading in the United States.
- December 4 – Former Minnesota farmer Oliver Hudson Kelley founds the Order of the Patrons of Husbandry (better known today as the Grange movement).