* Herbert Austin ( 1866 – 1941 ), British founder of the Austin Motor Company

* 1866 – The Grand Army of the Republic, an American patriotic organization composed of Union veterans of the American Civil War, is founded.

* 1866 – Felix-Raymond-Marie Rouleau, Canadian cardinal of the Roman Catholic Church ( d. 1931 )

* 1866 – Princess Viktoria of Prussia ( d. 1929 )

* 1866 – Allen Lard, American golfer ( death date unknown )

* 1866 – Giovanni Agnelli, Italian businessman, founded Fiat S. p. A ( d. 1945 )

* 1866 – Gábor Klauzál, Hungarian politician ( b. 1804 )

* 1866 – Matthew Henson, American explorer ( d. 1955 )

* 1866 – José de Diego, Puerto Rican statesman and journalist ( d. 1918 )

* 1866 – Charles Jean de la Vallée-Poussin, Belgian mathematician ( d. 1962 )

* 1866 – Italo Santelli, Italian fencer ( d. 1945 )

* 1866 – Jacinto Benavente, Spanish writer, Nobel Prize laureate ( d. 1954 )

* 1866 – Henrik Sillem, Dutch sports shooter ( d. 1907 )

* Alexander John Cuza, prince of Romania ( 1859 – 1866 )

* 1866 – Austro-Prussian War ends with the Treaty of Prague.

* 1866 – Anne Sullivan, American teacher, instructor and companion of Helen Keller ( d. 1936 )

* 1866 – Ernest Starling, British physiologist ( d. 1927 )

* 1866 – Italy and Prussia ally against the Austrian Empire.

* 1866 – The American Society for the Prevention of Cruelty to Animals ( ASPCA ) is founded in New York City by Henry Bergh.

He married fourthly at the Dolmabahçe Palace, Constantinople, on 21 September 1866 to Georgian HH Hayranidil Kadın Efendi ( Kars, 2 November 1846 – Ortaköy Palace, Constantinople, 26 November 1898 ), and had two children.

The Earl of Derby, Prime Minister 1852, 1858 – 59, 1866 – 68

Charles Erdman ( 1866 – 1960 ) advocated apostolic authorship and wrote that only the Apostle John fits the image of the author derived from the text.

#** Marie Laetitia Eugénie Catherine Adélaïde Bonaparte ( 1866 – 1926 )

Le déjeuner sur l ' herbe, ( right section ), with Gustave Courbet, 1865 – 1866, Musée d ' Orsay, Paris, France | Paris

Following the 1852 Telegraph Act, Canada's first permanent transatlantic telegraph link was a submarine cable built in 1866 between Ireland and Newfoundland. Telegrams were sent through networks built by Canadian Pacific and Canadian National.

The independent Princedom of Serbia, had conducted the first population census in 1834 ; the subsequent censuses were conducted in 1841, 1843, 1846, 1850, 1854, 1859, 1863 and 1866 and 1874.

" Dalhousie reopened with six professors and one tutor, and awarded its first degrees in 1866.

The term " ecology " () is of a more recent origin and was first coined by the German biologist Ernst Haeckel in his book Generelle Morphologie der Organismen ( 1866 ).

The first death due to cholera occurred in 1866, but by then Elizabeth had already opened St. Mary ’ s Dispensary for Women and Children, at 69 Seymour Place.

Perhaps the first elaborate and systematic exposition was by John Venn, in The Logic of Chance: An Essay on the Foundations and Province of the Theory of Probability ( published editions in 1866, 1876, 1888 ).

The first school and church opened in 1866, and the town was platted in 1867.

Sullivan's first foray into comic opera was Cox and Box ( 1866 ), written with librettist F. C. Burnand for an informal gathering of friends.

A new edition ( the first edition was resold in America ), released in December of the same year but carrying an 1866 date, was quickly printed and became an instant best-seller, securing Tenniel's lasting fame in the process.

* 1866 – Reconstruction: Tennessee becomes the first U. S. state to be readmitted to the Union following the American Civil War.

The Malmad, which was completed when its author was fifty-five years old, but was first published by the Meḳiẓe Nirdamim Society at Lyck in the year 1866, is really nothing but a volume of sermons, by which the author intended to stimulate study and to dispel intellectual blindness.

Kenesaw Mountain Landis (; November 20, 1866 – November 25, 1944 ) was an American jurist who served as a federal judge from 1905 to 1922 and as the first Commissioner of Baseball from 1920 until his death.

People with Down's Syndrome were first called " Mongolian " in 1866.

* The last Monday of May is Memorial Day in the United States, first celebrated on May 5, 1866, in Waterloo, New York.

* 1866 – Memorial Day first celebrated in United States at Waterloo, New York.

The Black Crook ( 1866 ), considered by some historians to be the first musical

Although de Marignac was able to produce tantalum-free niobium on a larger scale by 1866, it was not until the early 20th century that niobium was first used commercially, in incandescent lamp filaments.

These reforms included guarantees to ensure the Ottoman subjects perfect security for their lives, honour, and property ; the introduction of the first Ottoman paper banknotes ( 1840 ) and opening of the first post offices ( 1840 ); the reorganization of the finance system according to the French model ( 1840 ); the reorganization of the Civil and Criminal Code according to the French model ( 1840 ); the establishment of the Meclis-i Maarif-i Umumiye ( 1841 ) which was the prototype of the First Ottoman Parliament ( 1876 ); the reorganization of the army and a regular method of recruiting, levying the army, and fixing the duration of military service ( 1843 – 44 ); the adoption of an Ottoman national anthem and Ottoman national flag ( 1844 ); the first nationwide Ottoman census in 1844 ( only male citizens were counted ); the first national identity cards ( officially named the Mecidiye identity papers, or informally kafa kağıdı ( head paper ) documents, 1844 ); the institution of a Council of Public Instruction ( 1845 ) and the Ministry of Education ( Mekatib-i Umumiye Nezareti, 1847, which later became the Maarif Nezareti, 1857 ); the abolition of slavery and slave trade ( 1847 ); the establishment of the first modern universities ( darülfünun, 1848 ), academies ( 1848 ) and teacher schools ( darülmuallimin, 1848 ); establishment of the Ministry of Healthcare ( Tıbbiye Nezareti, 1850 ); the Commerce and Trade Code ( 1850 ); establishment of the Academy of Sciences ( Encümen-i Daniş, 1851 ); establishment of the Şirket-i Hayriye which operated the first steam-powered commuter ferries ( 1851 ); the first European style courts ( Meclis-i Ahkam-ı Adliye, 1853 ) and supreme judiciary council ( Meclis-i Ali-yi Tanzimat, 1853 ); establishment of the modern Municipality of Istanbul ( Şehremaneti, 1854 ) and the City Planning Council ( İntizam-ı Şehir Komisyonu, 1855 ); the abolition of the capitation ( Jizya ) tax on non-Muslims, with a regular method of establishing and collecting taxes ( 1856 ); non-Muslims were allowed to become soldiers ( 1856 ); various provisions for the better administration of the public service and advancement of commerce ; the establishment of the first telegraph networks ( 1847 – 1855 ) and railroads ( 1856 ); the replacement of guilds with factories ; the establishment of the Ottoman Central Bank ( originally established as the Bank-ı Osmanî in 1856, and later reorganized as the Bank-ı Osmanî-i Şahane in 1863 ) and the Ottoman Stock Exchange ( Dersaadet Tahvilat Borsası, established in 1866 ); the Land Code ( Arazi Kanunnamesi, 1857 ); permission for private sector publishers and printing firms with the Serbesti-i Kürşad Nizamnamesi ( 1857 ); establishment of the School of Economical and Political Sciences ( Mekteb-i Mülkiye, 1859 ); the Press and Journalism Regulation Code ( Matbuat Nizamnamesi, 1864 ); among others.