October 23 is the 296th day of the year (297th every 4 years) in the Gregorian calendar. There are 69 days remaining until the end of the year.

• 42 BC – Roman civil wars: Second Battle of Philippi – Mark Antony and Octavian defeat the army of Marcus Junius Brutus, who commits suicide shortly after.
• 425 – Valentinian III becomes Roman Emperor, at the age of 6.
• 1086 – Battle of az-Zallaqah: The army of Yusuf ibn Tashfa defeats forces of King Alfonso VI of Castile.
• 1157 – The Battle of Grathe-Heath ends the civil war in Denmark. King Sweyn III is killed and Valdemar I of Denmark takes over.
• 1295 – Scotland and France sign the first treaty of the 'Auld Alliance' in Paris, against England.
• 1520 – Charles V, Holy Roman Emperor is crowned in Aachen.
• 1642 – English Civil War: The Battle of Edgehill
• 1707 – The first parliament of Great Britain meets.
• 1739 – War of Jenkins' Ear: British Prime Minister Robert Walpole reluctantly declares war on Spain.
• 1812 – Charles Francois de Malet, a French general, begins a conspiracy to overthrow then-Emperor Napoleon Bonaparte, by falsely claiming that he (Napoleon) had died in his attempt to conquer Russia.
• 1850 – The first National Women's Rights Convention begins in Worcester, Massachusetts.
• 1864 – American Civil War: Union forces defeat the Confederates in the Battle of Westport.
• 1870 – Franco-Prussian War: The Siege of Metz concludes with a decisive Prussian victory.

• 1906 – Alberto Santos-Dumont flies an aircraft in the first heavier-than-air flight, in Paris.
• 1912 – The Battle of Kumanovo between Russian and Ottoman forces begins.
• 1915 – 25,000 to 33,000 women march on Fifth Avenue in New York City to advocate their right to vote.
• 1917 – Vladimir Lenin calls for the October Revolution in Russia.
• 1929 – Great Depression: The first signs of panic show.
• 1940 – Norwegian Hurtigruten passenger steamer Prinsesse Ragnhild sinks after an explosion off northern Norway, killing 299 people on board.
• 1941 – World War II: Georgy Zhukov takes command of the Red Army operation to prevent the Nazis' further advances into Russia.
• 1942 – World War II: The Second Battle of El Alamein takes place, as the British Eighth Army begins an offensive to expel the Axis armies from Egypt.
• 1942 – World War II: The Battle of Henderson Field begins in the Guadalcanal Campaign, lasting until October 26.
• 1944 – World War II: The Red Army enters Hungary.
• 1944 – World War II: The Battle of Leyte Gulf in the Philippines.
• 1946 – In New York, the UN General Assembly meets for the first time.
• 1956 – The Hungarian Revolution of 1956 against Soviet rule begins.
• 1958 – The Smurfs cartoons appear for the first time.
• 1958 – The Springhill Mine Bump mining disaster in Nova Scotia, killing 74 people, with 100 surviving the accident.
• 1970 – Gary Gabelich sets a land-speed record in a rocket–powered automobile called the Blue Flame, fueled by natural gas.
• 1972 – Vietnam War: Operation Linebacker – The US ends a bombing campaign of North Vietnam following the Easter Offensive.
• 1973 – A UN–sanctioned ceasefire officially ends the Yom Kippur War between Israel and Syria.
• 1983 – A truck bomb hits a US barracks in Lebanon, killing 241 troops. On the same day, another truck bomb hits a French barracks, killing 58 military personnel.
• 1989 – The Hungarian Republic is declared.
• 1989 – The Philips Disaster in Pasadena, Texas kills 23 people.
• 1992 – Akihito becomes the first Japanese Emperor to stand on Chinese soil.
• 1995 – Yolanda Saldivar is convicted of murdering the singer Selena on March 31 of the same year.

• 2001 – The iPod is released.
• 2002 – The Moscow Theatre Siege begins, as Chechen terrorists take around 700 theatregoers hostage.
• 2003 – The Walt Disney Concert Hall in Los Angeles, California, designed by Frank Gehry, is opened.
• 2004 – An earthquake in the Niigata Prefecture in Japan kills 35 people and injures around 2,200.
• 2005 – Hurricane Wilma hits the Yucatán, in Mexico.
• 2005 – Lech Kaczynski is elected President of Poland, ahead of Donald Tusk.
• 2011 – New Zealand wins the Rugby World Cup, defeating France 8–7 in Auckland.
• 2011 – Motorcycle rider Marco Simoncelli is killed in a crash at the Malaysian Moto GP.
• 2011 – A powerful magnitude 7.2 earthquake hits Van Province, in eastern Turkey.
• 2012 – The BBC ends its 38-year teletext service Ceefax, with Northern Ireland completing the United Kingdom's transition to digital television broadcasting.
• 2015 – Hurricane Patricia is measured as the heaviest hurricane ever to hit North or Central America, as it hits the Pacific Ocean coast of Mexico.
• 2015 – 43 people, mostly pensioners on a day-trip, die in a coach crash in Southwestern France, in one of the country's deadliest-ever road accidents.
• 2018 – The Hong Kong-Zhuhai–Macau Bridge is officially opened by Chinese Communist Party general secretary Xi Jinping.
• 2018 – October 2018 United States mail bombing attempts: A mail bomb addressed to former United States Secretary of State Hillary Clinton is caught by police, after one addressed to George Soros was caught the previous day.
• 2019 – The bodies of 39 people are found in a lorry trailer at Purfleet, Essex, England.

• 63 BC – Marcus Vipsanius Agrippa, Roman general (d. 12 BC)
• 1503 – Isabella of Portugal (d. 1539)
• 1516 – Charlotte of Valois, French princess (d. 1524)
• 1634 – Hedvig Eleonora of Holstein-Gottorp (d. 1715)
• 1654 – Johann Bernhard Staudt, Austrian Jesuit composer (d. 1712)
• 1713 – Pieter Burman the Younger, Dutch philologist (d. 1778)
• 1715 – Tsar Peter II of Russia (d. 1730)
• 1762 – Samuel Morey, American inventor (d. 1843)
• 1770 – George Ramsay, 9th Earl of Dalhousie, Scottish soldier and colonial administrator (d. 1838)
• 1771 – Jean-Andoche Junot, French general (d. 1813)
• 1796 – Stefano Franscini, Swiss Federal Councillor (d. 1857)
• 1801 – Albert Lortzing, German composer (d. 1851)
• 1813 – Ludwig Leichhardt, German explorer (d. 1848)
• 1815 – Joao Mauricio Wanderley, Brazilian magistrate and politician (d. 1889)
• 1817 – Pierre Athanase Larousse, French lexicographer (d. 1875)
• 1831 – Basil Lanneau Gilders Lane, American classical^{[disambiguation needed]} scholar (d. 1924)
• 1835 – Adlai E. Stevenson, Vice President of the United States (d. 1914)
• 1844 – Robert Bridges, English poet (d. 1930)
• 1857 – Juan Luna, Filipino painter (d. 1899)
• 1868 – Alfred Mond, 1st Baron Melchett, British industrialist, financier and politician (d. 1930)
• 1869 – John Heisman, American football player and coach (d. 1936)
• 1871 – Gjergj Fishta, Albanian poet (d. 1940)
• 1873 – William D. Coolidge, American physicist and inventor (d. 1975)
• 1875 – Gilbert N. Lewis, American chemist (d. 1946)
• 1876 – Franz Schlegelberger, German politician (d. 1970)
• 1880 – Una O'Connor, Irish actress (d. 1959)
• 1885 – Lawren Harris, Canadian painter (d. 1970)
• 1893 – Gummo Marx, American actor (d. 1977)
• 1894 – Rube Bressler, American baseball player (d. 1966)
• 1896 – Roman Jakobson, Russian-born linguist (d. 1982)
• 1896 – Lilyan Tashman, American actress (b. 1934)

• 1905 – Felix Bloch, Swiss physicist (d. 1983)
• 1905 – Gertrude Ederle, American swimmer (d. 2003)
• 1905 – Yen Chia-han, President of the Republic of China (d. 1993)
• 1908 – Ilya Frank, Russian physicist (d. 1990)
• 1910 – Richard Mortensen, Danish painter (d. 1993)
• 1910 – Hayden Rorke, American actor (d. 1987)
• 1911 – Jack Keller, American hurdler (d. 1978)
• 1918 – James Daly, American actor (d. 1978)
• 1919 – Manolis Andronikos, Greek archaeologist (d. 1992)
• 1920 – Lygia Clark, Brazilian artist (d. 1988)
• 1920 – Bob Montana, American cartoonist (d. 1975)
• 1922 – Jean Barker, Baroness Trumpington, English politician (d. 2018)
• 1922 – Coleen Gray, American actress (d. 2015)
• 1923 – Bhairon Singh Shekhawat, Vice President of India (d. 2010)
• 1925 – Manos Hadjidakis, Greek composer (d. 1994)
• 1925 – Johnny Carson, American television host (d. 2005)
• 1927 – Barron Hilton, American businessman (d. 2019)
• 1927 – Leszek Kolakowski, Polish philosopher (d. 2009)
• 1927 – Dezso Gyarmati, Hungarian water polo player (d. 2013)
• 1928 – Zhu Rongji, Chinese politician
• 1929 – Shamsur Rahman, Bangladeshi poet, columnist and journalist (d. 2006)
• 1931 – Diana Dors, British actress (d. 1984)
• 1931 – Jim Bunning, American baseball player and politician
• 1936 – Philip Kaufman, American director
• 1938 – H. John Heinz III, American politician (d. 1991)
• 1940 – Pelé, Brazilian footballer
• 1940 – Jane Holzer, American model, actress, producer and art collector
• 1941 – Lawrence Foster, American conductor
• 1941 – Igor Smirnov, Moldovan politician
• 1942 – Bernd Erdmann, German footballer
• 1942 – Michael Crichton, American writer (d. 2008)
• 1942 – Anita Roddick, British businesswoman (d. 2007)
• 1945 – Maggi Hambling, British painter and sculptor
• 1945 – Kim Larsen, Danish musician and singer (d. 2018)
• 1945 – Michel Vautrot, French football referee
• 1947 – Kazimierz Deyna, Polish footballer (d. 1989)
• 1947 – Abdel Aziz al-Rantissi, leader of Hamas (d. 2004)
• 1948 – Gerry Robinson, Irish businessman and television presenter
• 1949 – Michael Burston (Wurzel), British musician (Motorhead) (d. 2011)

• 1951 – Charly García, Argentine singer
• 1951 – Fatmir Sejdiu, former President of Kosovo
• 1951 – Angel de Andres Lopez, Spanish actor (d. 2016)
• 1952 – Ken Tipton, American entrepreneur, actor, director, writer and producer
• 1954 – Ang Lee, Taiwanese movie director
• 1954 – Uli Stein, German footballer
• 1956 – Dianne Reeves, American jazz singer
• 1956 – Dwight Yoakam, American singer-songwriter, guitarist and actor
• 1957 – Martin Luther King III, American activist
• 1957 – Paul Kagame, President of Rwanda
• 1959 – Sam Raimi, American movie director
• 1959 – "Weird Al" Yankovic, American musical parodist
• 1960 – Randy Pausch, American computer scientist and writer (d. 2008)
• 1961 – Andoni Zubizarreta, Spanish footballer
• 1962 – Stefano Colantuono, Italian footballer and coach
• 1963 – Rashidi Yekini, Nigerian footballer (d. 2012)
• 1964 – Robert Trujillo, American musician (Metallica)
• 1967 – Omar Linares, Cuban baseball player
• 1968 – Maria Darling, English voice actress
• 1969 – Trudi Canavan, Australian writer
• 1969 – Dolly Buster, Czech-German pornographic actress
• 1970 – Matthew Barzun, American diplomat
• 1971 – Bohuslav Sobotka, Czech politician, Prime Minister of the Czech Republic
• 1973 – Christian Dailly, Scottish footballer
• 1975 – Yoon Sun-ha, South Korean actress and singer

• 1976 – Cat Deeley, British television personality
• 1976 – Ryan Reynolds, Canadian actor
• 1978 – Jimmy Bullard, English footballer
• 1978 – Archie Thompson, Australian footballer
• 1978 – Steve Harmison, English cricketer
• 1978 – John Lackey, American baseball player
• 1979 – Simon Davies, Welsh footballer
• 1984 – Izabel Goulart, Brazilian model
• 1984 – Meghan McCain, American columnist and author
• 1985 – Masiela Lusha, Albanian-born American writer and actress
• 1985 – Lachlan Gillespie, Australian musician (The Wiggles)
• 1985 – Mohammed Abdellaoue, Norwegian footballer
• 1986 – Briana Evigan, American actress
• 1986 – Jessica Stroup, American actress
• 1986 – Emilia Clarke, English actress
• 1987 – Faye Hamlin, Swedish singer
• 1988 – Jordan Crawford, American basketball player
• 1989 – Andriy Yarmolenko, Ukrainian footballer
• 1990 – Paradise Oskar, Finnish singer
• 1991 – Princess Mako of Akishino of Japan
• 1992 – Alvaro Morata, Spanish footballer
• 1993 – Taylor Spreitler, American actress
• 1994 – Georgia Toffolo, English television personality
• 1997 – Daphne Blunt, American actress and singer
• 1998 – Amandla Stenberg, American actress

• 42 BC – Marcus Junius Brutus (suicide) (b. 85 BC)
• 877 – Ignatius, Greek Orthodox Patriarch of Constantinople (b. 797)
• 891 – Yazaman al-Khadim, Arab military leader
• 930 – Emperor Daigo of Japan (b. 885)
• 1157 – Sweyn III of Denmark (b. 1120)
• 1456 – Giovanni da Capistrano, Italian saint (b. 1381)
• 1581 – Michael Neander, German mathematician and astronomer (b. 1529)
• 1616 – Leonhard Hutter, German theologian (b. 1563)
• 1774 – Michel Benoist, French Jesuit missionary and scientist (b. 1715)
• 1869 – Edward Smith-Stanley, 14th Earl of Derby, Prime Minister of the United Kingdom (b. 1799)
• 1872 – Théophile Gautier, French writer (b. 1811)
• 1885 – Charles S. West, Texan jurist and politician (b. 1829)
• 1893 – Alexander Battenberg, Prince of Bulgaria (b. 1857)
• 1896 – Columbus Delano, American politician (b. 1809)

• 1910 – Chulalongkorn (Rama V), King of Siam (now Thailand) (b. 1853)
• 1915 – W. G. Grace, English cricketer (b. 1848)
• 1921 – John Boyd Dunlop, Scottish inventor (b. 1840)
• 1930 – Vicente Casanova y Marzol, Archbishop of Granada (b. 1854)
• 1938 – Jean-Guy Gautier, French rugby^{[disambiguation needed]} player (b. 1875)
• 1939 – Zane Grey, American writer (b. 1872)
• 1940 – George R. Cortelyou, American politician (b. 1862)
• 1944 – Charles Glover Barkla, English physicist (b. 1877)
• 1944 – Hana Brady, Czech Holocaust victim (b. 1931)
• 1948 – Carl Edward Bailey, Governor of Arkansas (b. 1894)
• 1950 – Al Jolson, American singer and actor (b. 1886)
• 1957 – Christian Dior, French fashion designer (b. 1905)
• 1959 – Gerda Lundequist, Swedish actress (b. 1871)
• 1979 – Antonio Caggiano, Argentine cardinal (b. 1889)
• 1983 – Jessica Savitch, journalist (b. 1947)
• 1984 – Oskar Werner, Austrian actor (b. 1922)
• 1986 – Edward Adelbert Doisy, American biochemist, won the 1843 Nobel Prize in Physiology or Medicine (b. 1893)
• 1988 – Asashio Taro III, Japanese sumo wrestler (b. 1929)
• 1989 – Armida, Mexican-American actress, singer and dancer (b. 1911)
• 1990 – Louis Althusser, French Marxist philosopher (b. 1918)
• 1994 – Robert Lansing, American actor (b. 1928)
• 1997 – Bert Haanstra, Dutch director, producer and screenwriter (b. 1916)
• 2000 – Rodney Adnoa'i, Samoan-American professional wrestler (b. 1966)

• 2003 – Tony Capstick, British actor, comedian, musician and broadcaster (b. 1944)
• 2003 – Soong May-ling, widow of Chiang Kai-shek (b. 1898)
• 2004 – George Silk, New Zealand-American photographer (b. 1916)
• 2005 – John Muth, American economist (b. 1930)
• 2009 – Lou Jacobi, Canadian actor (b. 1913)
• 2010 – David Thompson, Prime Minister of Barbados (b. 1961)
• 2011 – Nusrat Bhutto, former First Lady of Pakistan (b. 1929)
• 2011 – Marco Simoncelli, Italian motorcycle racer (b. 1987)
• 2011 – Herbert A. Hauptman, American mathematician and Nobel Prize–winning chemist (b. 1917)
• 2011 – John McCarthy, American computer scientist (b. 1927)
• 2011 – Bronislovas Lubys, former Prime Minister of Lithuania (b. 1938)
• 2012 – Sunil Gangopadhyay, Indian novelist and poet (b. 1934)
• 2012 – Wilhelm Brasse, Polish photographer (b. 1917)
• 2013 – Bill Mazer, American TV and radio presenter (b. 1920)
• 2013 – Anthony Caro, British sculptor (b. 1924)
• 2014 – Alvin Stardust, British singer (b. 1942)
• 2014 – Ghulam Azam, Bangladeshi politician (b. 1922)
• 2014 – John Bramlett, American football player (b. 1941)
• 2014 – Bernard Mayes, British author and broadcaster (b. 1929)
• 2014 – André Piters, Belgian footballer (b. 1931)
• 2014 – Tullio Regge, Italian physicist (b. 1931)
• 2015 – Krunoslav Hulak, Croatian chess player (b. 1951)
• 2015 – Leon Bibb, American folk singer (b. 1922)
• 2015 – Paride Tumburus, Italian footballer (b. 1939)
• 2015 – Jimmy Roberts, Canadian ice hockey player (b. 1946)
• 2016 – Jimmy Perry, English actor and screenwriter (b. 1923)
• 2016 – Pete Burns, English singer-songwriter (b. 1959)
• 2016 – Khalifa bin Hamad Al Thani, former Emir of Qatar (b. 1932)
• 2017 – Walter Lassally, German-born British-Greek cinematographer (b. 1926)
• 2017 – Paul J. Weitz, American pilot and astronaut (b. 1932)
• 2018 – Skip Campbell, American politician (b. 1948)
• 2018 – James Karen, American actor (b. 1923)
• 2018 – Alojz Rebula, Italian-Slovenian writer, playwright and essayist (b. 1924)
• 2018 – Laurens van Ravens, Belgian football referee (b. 1922)
• 2019 – Santos Juliá, Spanish historian and sociologist (b. 1940)
• 2019 – James W. Montgomery, American Episcopalian prelate (b. 1921)
• 2019 – Alfred Znamierowski, Polish vexillologist (b. 1940)

• Mole Day (Chemists)
• Chulalongkorn Day (Thailand)
• National Day of Hungary
• Day of the Macedonian Revolutionary Struggle

Wikimedia Commons has media related to 23 October.