December 21 is the 355th day of the year (356th in leap years) in the Gregorian calendar. There are 10 days remaining until the end of the year.
- 69 - The end of the Year of the four emperors: Following Galba, Otho and Vitellius, Vespasian becomes the fourth Emperor of Rome within a year.
- 1598 - Battle of Curalaba: The revolting Mapuche, led by cacique Pelentaru, inflict a major defeat on Spanish troops in southern Chile; all Spanish cities south of the Biobio river are eventually taken by the Mapuches, and all conquest of Mapuche territories by Europeans practically ceases, until the 1870s "Pacification of Araucania".
- 1620 - Plymouth Colony: William Bradford and the Mayflower Pilgrims land on what is now known as Plymouth Rock in Plymouth, Massachusetts.
- 1844 - The Rochdale Pioneers commence business at their cooperative in Rochdale, England, starting the Cooperative movement.
- 1861 - Medal of Honor: Public Resolution 82, containing a provision for a Navy Medal of Valor, is signed into law by President Abraham Lincoln.
- 1872 - Challenger expedition: HMS Challenger, commanded by Captain George Nares, sails from Portsmouth.
- 1883 - The first Permanent Force cavalry and infantry regiments of the Canadian Army are formed: The Royal Canadian Dragoons and The Royal Canadian Regiment.
- 1913 - Arthur Wynne's "word-cross", the first crossword puzzle, is published in the New York World.
- 1958 - French presidential election: Charles de Gaulle is elected President of France as his Union des Démocrates pour la République party gain 78.5% of the vote.
- 1962 - Rondane National Park is established as Norway's first national park.
- 1967 - Louis Washkansky, the first man to undergo a heart transplant, dies in Cape Town, South Africa, after living for 18 days.
- 1968 - Apollo program: Apollo 8, the first manned mission to the moon, is launched from the Kennedy Space Center in Florida. At 2h:50m:37s Mission elapsed time (MES), the crew performs the first ever manned Trans Lunar Injection and become the first humans to leave Earth's gravity.
- 1971 - The United Nations Security Council chooses Kurt Waldheim to succeed U Thant as Secretary-General.
- 1973 - The Geneva Conference on the Arab-Israeli conflict opens.
- 1979 - Lancaster House Agreement: An independence agreement for Rhodesia is signed in London by Lord Carrington, Sir Ian Gilmour, Robert Mugabe, Joshua Nkomo, Bishop Abel Muzorewa and S.C. Mundawarara.
- 1988 - A bomb explodes on board Pan Am flight 103 over Lockerbie, Dumfries and Galloway, Scotland, killing 270.
- 1989 - The Romanian Revolution of 1989 moves from Timişoara to Bucharest.
- 1992 - A Dutch DC-10, flight Martinair MP 495, crashes at Faro Airport (Portugal), killing 56 people.
- 1995 - The city of Bethlehem passes from Israeli to Palestinian control.
- 1999 - The Spanish Civil Guard intercepts a van loaded with 950 kg of explosives that ETA intended to use to blow up Torre Picasso in Madrid.
- 2007 - The Schengen Agreement area increases to include 9 European Union member states; Czech Republic, Estonia, Hungary, Latvia, Lithuania, Malta, Poland, Slovakia, and Slovenia on land and sea borders.
- 1118 - Thomas Becket, Lord Chancellor of England and Archbishop of Canterbury (d. 1170)
- 1401 - Tommaso Masaccio, Italian painter (d. 1428)
- 1596 - Petro Mohyla, Moldovan Orthodox Metropolitan Bishop of Kiev and Galicia (d. 1646)
- 1603 - Roger Williams, English theologian and colonist (d. 1684)
- 1714 - John Bradstreet, Canadian-born soldier (d. 1774)
- 1778 - Anders Sandøe Ørsted, Danish politician (d. 1860)
- 1795 - Leopold von Ranke, German historian (d. 1886)
- 1804 - Benjamin Disraeli, 1st Earl of Beaconsfield, Prime Minister of the United Kingdom (d. 1881)
- 1805 - Thomas Graham, British chemist (d. 1869)
- 1811 - Archibald Campbell Tait, Archbishop of Canterbury (d. 1882)
- 1815 - Thomas Couture French painter and teacher (d. 1879)
- 1818 - Amalia of Oldenburg, Queen of Greece (d. 1875)
- 1832 - John H. Ketcham, American politician (d. 1906)
- 1843 - Thomas Bracken, Irish-born New Zealand poet (d. 1898)
- 1850 - Zdeněk Fibich, Bohemian composer (d. 1900)
- 1850 - William Wallace Lincoln, son of U.S. president Abraham Lincoln (d. 1862)
- 1851 - Thomas Chipman McRae, American politician, 34th Governor of Arkansas (d. 1929)
- 1859 - Gustave Kahn, French poet (d. 1936)
- 1872 - Sidney Ainsworth, British actor (d. 1922)
- 1872 - Don Lorenzo Perosi, Italian composer (d. 1956)
- 1872 - Albert Payson Terhune, American author (d. 1942)
- 1873 - Blagoje Bersa, Croatian composer (d. 1934)
- 1876 - Jack Lang (John Thomas Lang), Premier of New South Wales (d. 1975)
- 1878 - Jan Łukasiewicz, Polish philosopher and mathematician (d. 1956)
- 1879 - Joseph Stalin, U.S.S.R. Leader (d. 1953)
- 1885 - Frank Patrick, Canadian hockey player (d. 1960)
- 1889 - Sewall Wright, American biologist (d. 1988)
- 1890 - Hermann Joseph Muller, American geneticist and Nobel laureate (d. 1967)
- 1891 - John William McCormack, American politician (d. 1980)
- 1892 - Amy Key Clarke, English mystical poet (d. 1980)
- 1892 - Walter Hagen, American golfer (d. 1969)
- 1892 - Rebecca West, British writer (d. 1983)
- 1896 - Leroy Robertson, American composer (d. 1971)
- 1905 - Anthony Powell, British author (d. 2000)
- 1909 - Seicho Matsumoto, Japanese mystery writer and journalist (d. 1992)
- 1911 - Josh Gibson, American baseball player (d. 1947)
- 1914 - Ivan Generalić, Austro-Hungarian-born Croatian painter (d. 1992)
- 1915 - Werner von Trapp, member of the Trapp Family Singers (d. 2007)
- 1917 - Heinrich Böll, German writer and Nobel laureate (d. 1985)
- 1917 - Sophie Masloff, American politician
- 1918 - Donald Regan, American White House Chief of Staff (d. 2003)
- 1918 - Kurt Waldheim, Austrian United Nations Secretary-General and Federal President of Austria (d. 2007)
- 1920 - Alicia Alonso, Cuban ballerina
- 1920 - Bob Bindig, American cartoonist (d. 2006)
- 1920 - Jean Gascon, Canadian actor (d. 1988)
- 1921 - Maila Nurmi, aka Vampira, Finnish-born American actress (d. 2008)
- 1921 - John Severin, American comics artist
- 1922 - Paul Winchell, American ventriloquist (d. 2005)
- 1922 - Itubwa Amram, Nauruan pastor and politician (d. 1989)
- 1923 - Intizar Hussain, Urdu writer and columnist of Pakistan
- 1926 - Joe Paterno, American football coach
- 1932 - Edward Hoagland, American essayist
- 1935 - John G. Avildsen, American film director
- 1935 - Lorenzo Bandini, Italian racecar driver (d. 1967)
- 1935 - Yusuf Bey (Joseph Stephens), American activist (d. 2003)
- 1935 - Phil Donahue, American talk show host
- 1935 - Edward Schreyer, Canadian politician, Premier of Manitoba
- 1937 - Jane Fonda, American actress
- 1937 - Donald F. Munson, American politician
- 1938 - Frank Moorhouse, Australian author
- 1939 - Lloyd Axworthy, Canadian politician
- 1940 - Frank Zappa, American musician (d. 1993)
- 1940 - Ray Hildebrand, American singer (Paul & Paula)
- 1942 - Hu Jintao, Chinese president
- 1942 - Reinhard Mey, German singer
- 1942 - Carla Thomas, American singer
- 1943 - André Arthur. Quebec radio host
- 1943 - Albert Lee, English guitarist
- 1944 - Zheng Xiaoyu, Chinese bureaucrat (d. 2007)
- 1944 - Bill Atkinson, English footballer
- 1944 - Michael Tilson Thomas, American conductor
- 1946 - Christopher Keene, American conductor (d. 1995)
- 1946 - Carl Wilson, American musician (The Beach Boys) (d. 1998)
- 1947 - Bryan Hamilton, Northern Irish footballer
- 1947 - Paco de Lucía, Spanish musician
- 1948 - Samuel L. Jackson, American actor
- 1948 - Dave Kingman, American baseball player
- 1948 - Willi Resetarits, Austrian musician
- 1949 - Nikolaos Sifounakis, Greek politician
- 1950 - Jeffrey Katzenberg, American film producer
- 1950 - Lillebjørn Nilsen, Norwegian singer-songwriter
- 1951 - Nick Gilder, English musician (Sweeney Todd)
- 1952 - Joaquín Andújar, Dominican baseball player
- 1953 - Betty Wright, American singer
- 1954 - Chris Evert, American tennis player
- 1955 - Jane Kaczmarek, American actress
- 1955 - Kazuyuki Sekiguchi, Japanese musician
- 1957 - Tom Henke, American baseball player
- 1957 - Ray Romano, Italian-American comedian
- 1959 - Florence Griffith Joyner, American sprinter (d. 1998)
- 1960 - Louis Demetrius Alvanis, London-based pianist
- 1960 - Roger McDowell, American Major League Baseball Pitcher
- 1960 - Andy Van Slyke, American baseball player
- 1961 - Francis Ng, Hong Kong actor
- 1961 - Ryuji Sasai, Japanese composer
- 1964 - Rob Kelly, English football manager
- 1964 - Fabiana Udenio, Argentine actress
- 1965 - Andy Dick, American actor and comedian
- 1965 - Anke Engelke, German comedian
- 1966 - Kiefer Sutherland, British-born Canadian actor
- 1966 - Karri Turner, American actress
- 1967 - Ervin Johnson, American basketball player
- 1967 - Terry Mills, American basketball player
- 1967 - Mikhail Saakashvili, Soviet-born President of Georgia
- 1969 - Julie Delpy, French actress
- 1969 - Mihails Zemļinskis, Latvian footballer
- 1971 - Mathieu Chedid, French musician
- 1971 - Fenton Keogh, Australian celebrity chef
- 1971 - Brett Scallions, American singer (Fuel, The X's)
- 1972 - Gloria De Piero, English journalist
- 1972 - Latroy Hawkins, American baseball player
- 1972 - Dustin Hermanson, American baseball player
- 1972 - Erwin Schrott, Uruguayan opera singer
- 1973 - Karmen Stavec, German-born Slovenian singer
- 1973 - Mike Alstott, American football player
- 1973 - Irakli Alasania,Georgian politician and diplomat
- 1974 - Karrie Webb, Australian golfer
- 1975 - Paloma Herrera, Argentine ballet dancer
- 1976 - Mirela Manjani, Greek javelin thrower
- 1976 - Lukas Rossi Lead Singer for Supernova
- 1977 - Toby Rand Lead Singer for Juke Kartel
- 1978 - Mike Vitar, American actor
- 1979 - Tuva Novotny, Swedish actress and singer
- 1980 - Royce Ring, American Major League Baseball Player
- 1981 - Frankie Abernathy, American actress, The Real World: San Diego (d. 2007)
- 1981 - Sajid Mahmood, English cricketer
- 1981 - Lynda Thomas, Mexican singer
- 1981 - Cristian Zaccardo, Italian football player
- 1982 - Mike Gansey, American basketball player
- 1982 - Erica Hayden, American journalist and radio personality
- 1982 - Philip Humber, American baseball player
- 1982 - Iljo Keisse, Belgian cyclist
- 1984 - Darren Potter, Irish football player
- 1984 - Jackson Rathbone, American Actor
- 1985 - James Stewart Jr., American motorcycle racer
- 1987 - Brad Howard, Australian rules footballer
- 1987 - Valerie Concepcion, Filipino Actress
- 72 - Thomas the Apostle
- 1295 - Marguerite Berenger of Provence, wife of Louis IX of France (b. c.1221)
- 1308 - Henry I of Hesse (b. 1244)
- 1375 - Giovanni Boccaccio, Italian writer (b. 1313)
- 1504 - Bertold von Henneberg-Römhild, German archbishop and elector (b. 1442)
- 1549 - Marguerite of Navarre, wife of Henry II of Navarre (b. 1492)
- 1579 - Vicente Masip, Spanish painter
- 1597 - Petrus Canisius, Dutch Jesuit (b. 1521)
- 1807 - John Newton, English cleric and hymnist (b. 1725)
- 1824 - James Parkinson, English physician, geologist, paleontologist, and political activist (b. 1755)
- 1873 - Francis Garnier, French explorer (b. 1839)
- 1889 - Friedrich August von Quenstedt, German geologist (b. 1809)
- 1900 - Roger Wolcott, American political figure, 39th Governor of Massachusetts (b. 1847)
- 1933 - Knud Johan Victor Rasmussen, Greenlandic polar explorer and anthropologist (b. 1879)
- 1935 - Kurt Tucholsky, German journalist and satirist (b. 1890)
- 1937 - Frank B. Kellogg, United States Secretary of State, recipient of the Nobel Peace Prize (b. 1856)
- 1940 - F. Scott Fitzgerald, American writer (b. 1896)
- 1945 - George S. Patton, U.S. general (b. 1885)
- 1957 - Eric Coates, English composer (b. 1886)
- 1958 - Lion Feuchtwanger, German writer (b. 1884)
- 1959 - Rosanjin, Japanese calligrapher, restaurateur and ceramicist (b. 1883)
- 1964 - Carl Van Vechten, American writer and photographer (b. 1880)
- 1963 - Jack Hobbs, English cricketer (b. 1882)
- 1965 - Claude Champagne, Quebec composer (b. 1891)
- 1967 - Stuart Erwin, American actor (b. 1903)
- 1974 - James Henry Govier, British artist (b. 1910)
- 1974 - Richard Long, American actor (b. 1927)
- 1981 - Allan Dwan, Canadian-born American director and screenwriter (b. 1885)
- 1983 - Paul de Man, Belgian-born literary critic (b. 1919)
- 1987 - John Spence, founding No Doubt member (b. 1969)
- 1988 - Nikolaas Tinbergen, Dutch ornithologist, recipient of the Nobel Prize in Physiology or Medicine (b. 1907)
- 1990 - Clarence "Kelly" Johnson, American aeronautical engineer (Lockheed Skunk Works (b. 1910)
- 1992 - Albert King, American blues musician (b. 1924)
- 1992 - Nathan Milstein, Ukrainian violinist (b. 1903)
- 1997 - Amie Comeaux, American country music singer (b. 1976)
- 1998 - Roger Avon, Durham actor (b. 1914)
- 1998 - Karl Denver, Scottish singer (b. 1931)
- 1998 - Ernst Gunther Schenck, German doctor who joined the Sturmabteilung in 1933 (b. 1904)
- 2001 - Dick Schaap, American sports journalist (b. 1934)
- 2003 - Prince Alfonso of Hohenlohe-Langenburg, Spanish playboy and businessman (b. 1924)
- 2004 - Autar Singh Paintal, Indian medical scientist (b. 1925)
- 2005 - Elrod Hendricks, American baseball player and coach (b. 1940)
- 2006 - Scobie Breasley, Australian jockey (b. 1914)
- 2006 - Saparmurat Niyazov, President of Turkmenistan (b. 1940)
- 2007 - Ken Hendricks, American businessman (b. 1941)
