|Centuries:||18th century – 19th century – 20th century|
|Decades:||1810s 1820s 1830s – 1840s – 1850s 1860s 1870s|
|Years:||1842 1843 1844 – 1845 – 1846 1847 1848|
Year 1845 (MDCCCXLV) was a common year starting on Wednesday (link will display the full calendar) of the Gregorian Calendar (or a common year starting on Monday of the 12-day slower Julian calendar).
Events of 1845
January - June
- January 23 - The U.S. Congress establishes a uniform date for federal elections, which will henceforth be held on the first Tuesday after the first Monday in November.
- January 29 - " The Raven" by Edgar Allan Poe is published for the first time ( New York Evening Mirror).
- February 7 - In the British Museum, drunken visitor smashes Portland Vase - it takes months to repair
- February 28 - Texas becomes a state of the United States
- March 1 - President John Tyler signs a bill authorizing the United States to annex the Republic of Texas.
- March 3 - Florida is admitted as the 27th U.S. state.
- March 4 - For the first time the U.S. Congress passes legislation overriding a presidential veto.
- March 4 - James K. Polk succeeds John Tyler as the 11th President of the United States.
- March 11 - Flagstaff War: Chiefs Kawiti and Hone Heke lead 700 Māoris in the burning of the British colonial settlement of Kororareka, now known as Russell.
- March 13 - The premiere of the Violin Concerto by Felix Mendelssohn is given in Leipzig with Ferdinand David as soloist.
- March 17 - The rubber band is invented in England
- April 10 - A great fire destroys much of the city of Pittsburgh, Pennsylvania
- May 20 - The HMS Erebus and Terror with 134 men under John Franklin sail from the River Thames beginning a disastrous expedition to find the Northwest Passage.
- June 8 - Former United States President Andrew Jackson dies near Nashville, Tennessee.
July - December
- July 4 - Near Concord, Massachusetts, Henry David Thoreau embarks on a two-year experiment in simple living at Walden Pond (see Walden).
- July 20 - Charles Sturt enters the Simpson Desert in central Australia
- August 9 - Aberdeen Act signed.
- August 28 - Scientific American begins publication
- September 25 - Phi Alpha Literary Society founded.
- October 9 - The eminent and controversial Anglican, John Henry Newman, is received into the Roman Catholic Church
- October 10 - In Annapolis, Maryland, the Naval School (later renamed the United States Naval Academy) opens with 50 midshipmen students and seven professors.
- October 12 - The Société Mathématique de France was founded.
- October 13 - A majority of voters in the Republic of Texas approve a proposed constitution, that if accepted by the U.S. Congress, will make Texas a U.S. state.
- November 20 - Battle of Vuelta de Obligado between the Argentine Confederation and an Anglo-French fleet on the waters of the Paraná River.
- December 2 - Manifest Destiny: US President James Polk announces to Congress that the Monroe Doctrine should be strictly enforced and that the United States should aggressively expand into the West.
- December 5 - Templars of Honour and Temperance founded.
- December 6 - Alpha Sigma Phi Fraternity founded.
- December 22– December 23 - Battle of Ferozeshah: British forces defeat Sikhs in Punjab.
- December 27 - Anesthesia is used for childbirth for the first time (Dr. Crawford Williamson Long in Jefferson, Georgia).
- December 29 - Texas is admitted as the 28th U.S. state.
- December 30 - Queen's Colleges of Belfast, Cork and Galway are incorporated in Ireland.
- Second separation of Republic of Yucatan from Mexico
- Beginning of the Great Irish Famine.
- Ephraim Bee reveals that the Emperor of China has given him a special dispensation; that he had entrusted him with certain sacred and mysterious rituals through Caleb Cushing, the US Commissioner to China, to "extend the work and influence of the Ancient and Honorable Order of E Clampus Vitus" in the new world.
- Templars of Honour and Temperance established in U.S.
- Frederick Douglass's autobiography Narrative of the Life of Frederick Douglass, an American Slave is first published.
- Great Irish Famine (1844-1849)
|Ab urbe condita||2598|
|British Regnal year||8 Vict. 1 – 9 Vict. 1|
|Chinese calendar|| 甲辰年十一月廿三日
— to —乙巳年十二月初三日
|- Vikram Samvat||1901–1902|
|- Shaka Samvat||1767–1768|
|- Kali Yuga||4946–4947|
|- Ǹrí Ìgbò||845–846|
|Japanese calendar|| Kōka 2
|Juche calendar||N/A (before 1912)|
|Julian calendar||Gregorian minus 12 days|
|Minguo calendar||67 before ROC
|Thai solar calendar||2388|
- February 14 - Quintin Hogg, British philanthropist (d. 1903)
- February 15 - Elihu Root, American statesman and diplomat, recipient of the Nobel Peace Prize (d. 1937)
- February 25 - George Reid, fourth Prime Minister of Australia (d. 1918)
- March 3 - Georg Cantor, German mathematician (d. 1918)
- March 10 - Emperor Alexander III of Russia (d. 1894)
- March 20 - Victor Child Villiers, 7th Earl of Jersey, 18th Governor of New South Wales (d. 1915)
- March 27 - Wilhelm Conrad Röntgen, German physicist, Nobel Prize laureate (d. 1923)
- April 24 - Carl Spitteler, Swiss writer, Nobel Prize laureate (d. 1924)
- May 12 - Gabriel Fauré, French composer (d. 1924)
- May 16 - Ilya Ilyich Mechnikov, Russian microbiologist, recipient of the Nobel Prize in Physiology or Medicine (d. 1916)
- May 17 - Jacint Verdaguer, Catalan poet (d. 1902)
- May 25 - Eugène Grasset, Swiss-born artist (d. 1917)
- May 30 - King Amadeus I of Spain (d. 1890)
- June 7 - Leopold Auer, Hungarian violinist and composer (d. 1930)
- June 16 - Heinrich Dressel, German archaeologist (d. 1920)
- June 18 - Charles Louis Alphonse Laveran, French physician, recipient of the Nobel Prize in Physiology or Medicine (d. 1922)
- July 4 - Thomas John Barnardo, Irish philanthropist (d. 1905)
- July 18 - Tristan Corbière, French poet (d. 1875)
- July 19 - Horatio Nelson Young, American naval hero (d. 1913)
- August 10 - Abai Kunanbaev, Kazak poet (d. 1904)
- August 19 - Edmond James de Rothschild, French philanthropist (d. 1934)
- August 25 - King Ludwig II of Bavaria (d. 1886)
- November 3 - Edward Douglass White, 9th Chief Justice of the United States (d. 1921)
- November 4 - Vasudeo Balwant Phadke, Indian revolutionary (d. 1883)
- November 10 - John Sparrow David Thompson, Prime Minister of Canada (d. 1894)
- March 18 - Johnny Appleseed, pioneer (b. 1774)
- April 10 - Dr Thomas Sewall, American anatomist (b. 1786)
- May 12 - Janos Bacsanyi, Hungarian poet (b. 1763)
- June 4 - Lasse-Maja, notorious Swedish criminal (b. 1785)
- June 8 - Andrew Jackson, 7th President of the United States (b. 1767)
- July 12 - Henrik Wergeland, Norwegian writer (b. 1808)
- July 17 - Charles Grey, 2nd Earl Grey, Prime Minister of the United Kingdom (b. 1764)
- August 23 - Rafael Urdaneta, hero of Latin American war of independence (b. 1788)
- October 12 - Elizabeth Fry, British humanitarian (b. 1780)