| 138931 | December 9 | Event | 1775 – American Revolutionary War: British troops lose the Battle of Great Bridge, and leave Virginia soon afterward. |
| 138932 | December 9 | Event | 1793 – New York City's first daily newspaper, the American Minerva, is established by Noah Webster. |
| 138933 | December 9 | Event | 1824 – Patriot forces led by General Antonio José de Sucre defeat a Royalist army in the Battle of Ayacucho, putting an end to the Peruvian War of Independence. |
| 138934 | December 9 | Event | 1835 – Texas Revolution: The Texian Army captures San Antonio, Texas. |
| 138935 | December 9 | Event | 1851 – The first YMCA in North America is established in Montreal. |
| 138936 | December 9 | Event | 1856 – The Iranian city of Bushehr surrenders to occupying British forces. |
| 138937 | December 9 | Event | 1861 – American Civil War: The Joint Committee on the Conduct of the War is established by the U.S. Congress. |
| 138938 | December 9 | Event | 1872 – In Louisiana, P. B. S. Pinchback becomes the first serving African-American governor of a U.S. state. |
| 138939 | December 9 | Event | 1875 – The Massachusetts Rifle Association, "America's Oldest Active Gun Club", is founded. |
| 138940 | December 9 | Event | 1888 – Statistician Herman Hollerith installs his computing device at the United States War Department. |
| 138941 | December 9 | Event | 1897 – Activist Marguerite Durand founds the feminist daily newspaper La Fronde in Paris. |
| 138942 | December 9 | Event | 1905 – In France, the law separating church and state is passed. |
| 138943 | December 9 | Event | 1911 – A mine explosion near Briceville, Tennessee, kills 84 miners despite rescue efforts led by the United States Bureau of Mines. |
| 138944 | December 9 | Event | 1917 – World War I: Field Marshal Allenby captures Jerusalem, Palestine. |
| 138945 | December 9 | Event | 1922 – Gabriel Narutowicz is elected the first president of Poland. |
| 138946 | December 9 | Event | 1931 – The Constituent Cortes approves a constitution which establishes the Second Spanish Republic. |
| 138947 | December 9 | Event | 1935 – Walter Liggett, American newspaper editor and muckraker, is killed in a gangland murder. |
| 138948 | December 9 | Event | 1935 – The Downtown Athletic Club Trophy, later renamed the Heisman Trophy, is awarded for the first time. The winner is halfback Jay Berwanger of the University of Chicago. |
| 138949 | December 9 | Event | 1937 – Second Sino-Japanese War: Battle of Nanking – Japanese troops under the command of Lt. Gen. Asaka Yasuhiko launch an assault on the Chinese city of Nanjing (Nanking). |
| 138950 | December 9 | Event | 1940 – World War II: Operation Compass – British and Indian troops under the command of Major-General Richard O'Connor attack Italian forces near Sidi Barrani in Egypt. |
| 138951 | December 9 | Event | 1941 – World War II: The Republic of China, Cuba, Guatemala, and the Philippine Commonwealth, declare war on Germany and Japan. |
| 138952 | December 9 | Event | 1941 – World War II: The American 19th Bombardment Group attacks Japanese ships off the coast of Vigan, Luzon. |
| 138953 | December 9 | Event | 1946 – The "Subsequent Nuremberg trials" begin with the "Doctors' trial", prosecuting physicians and officers alleged to be involved in Nazi human experimentation and mass murder under the guise of euthanasia. |
| 138954 | December 9 | Event | 1946 – The Constituent Assembly of India meets for the first time to write the Constitution of India. |
| 138955 | December 9 | Event | 1950 – Cold War: Harry Gold is sentenced to 30 years in jail for helping Klaus Fuchs pass information about the Manhattan Project to the Soviet Union. His testimony is later instrumental in the prosecution of Julius and Ethel Rosenberg. |
| 138956 | December 9 | Event | 1953 – Red Scare: General Electric announces that all communist employees will be discharged from the company. |
| 138957 | December 9 | Event | 1956 – Trans-Canada Air Lines Flight 810, a Canadair North Star, crashes near Hope, British Columbia, Canada, killing all 62 people on board. |
| 138958 | December 9 | Event | 1958 – The John Birch Society is founded in the United States. |
| 138959 | December 9 | Event | 1960 – The first episode of Coronation Street, the world's longest-running television soap opera, is broadcast in the United Kingdom. |
| 138960 | December 9 | Event | 1961 – Tanganyika becomes independent from Britain. |