| 94831 | August 21 | Event | 1914 – World War I: The Battle of Charleroi, a successful German attack across the River Sambre which pre-empted a French offensive in the same area. |
| 94832 | August 21 | Event | 1918 – World War I: The Second Battle of the Somme begins. |
| 94833 | August 21 | Event | 1942 – World War II: The flag of Nazi Germany is installed atop the Mount Elbrus, the highest peak of the Caucasus mountain range. |
| 94834 | August 21 | Event | 1942 – World War II: The Guadalcanal Campaign: American forces defeat an attack by Imperial Japanese Army soldiers in the Battle of the Tenaru. |
| 94835 | August 21 | Event | 1944 – Dumbarton Oaks Conference, prelude to the United Nations, begins. |
| 94836 | August 21 | Event | 1944 – World War II: Canadian and Polish units capture the strategically important town of Falaise, Calvados, France. |
| 94837 | August 21 | Event | 1945 – Physicist Harry K. Daghlian, Jr. is fatally irradiated in a criticality accident during an experiment with the Demon core at Los Alamos National Laboratory. |
| 94838 | August 21 | Event | 1957 – The Soviet Union successfully conducts a long-range test flight of the R-7 Semyorka, the first intercontinental ballistic missile. |
| 94839 | August 21 | Event | 1959 – United States President Dwight D. Eisenhower signs an executive order proclaiming Hawaii the 50th state of the union. Hawaii's admission is currently commemorated by Hawaii Admission Day |
| 94840 | August 21 | Event | 1961 – Motown releases what would be its first #1 hit, "Please Mr. Postman" by The Marvelettes. |
| 94841 | August 21 | Event | 1963 – Xá Lợi Pagoda raids: The Army of the Republic of Vietnam Special Forces loyal to Ngô Đình Nhu, brother of President Ngo Dinh Diem, vandalizes Buddhist pagodas across the country, arresting thousands and leaving an estimated hundreds dead. |
| 94842 | August 21 | Event | 1968 – Nicolae Ceaușescu, leader of Communist Romania, publicly condemns the Soviet led Warsaw Pact invasion of Czechoslovakia, encouraging the Romanian population to arm itself against possible Soviet reprisals. |
| 94843 | August 21 | Event | 1968 – James Anderson, Jr. posthumously receives the first Medal of Honor to be awarded to an African American U.S. Marine. |
| 94844 | August 21 | Event | 1969 – An Australian, Denis Michael Rohan, sets the Al-Aqsa Mosque on fire, a major catalyst of the formation of the Organisation of Islamic Cooperation. |
| 94845 | August 21 | Event | 1971 – A bomb exploded in the Liberal Party campaign rally in Plaza Miranda, Manila, Philippines with several anti-Marcos political candidates injured. |
| 94846 | August 21 | Event | 1976 – Operation Paul Bunyan at Panmunjom, South Korea. |
| 94847 | August 21 | Event | 1979 – Soviet dancer Alexander Godunov defects to the United States. |
| 94848 | August 21 | Event | 1982 – Lebanese Civil War: The first troops of a multinational force lands in Beirut to oversee the Palestine Liberation Organization's withdrawal from Lebanon. |
| 94849 | August 21 | Event | 1983 – Philippine opposition leader Benigno Aquino, Jr. is assassinated at the Manila International Airport (now renamed Ninoy Aquino International Airport in his honor). |
| 94850 | August 21 | Event | 1986 – Carbon dioxide gas erupts from volcanic Lake Nyos in Cameroon, killing up to 1,800 people within a 20-kilometer range. |
| 94851 | August 21 | Event | 1991 – Latvia declares renewal of its full independence after the occupation of Soviet Union. |
| 94852 | August 21 | Event | 1991 – Coup attempt against Mikhail Gorbachev collapses. |
| 94853 | August 21 | Event | 1992 – Ruby Ridge Standoff in Idaho |
| 94854 | August 21 | Event | 1993 – NASA loses contact with the Mars Observer spacecraft. |
| 94855 | August 21 | Event | 2001 – NATO decides to send a peace-keeping force to the former Yugoslav Republic of Macedonia. |
| 94856 | August 21 | Event | 2001 – The Red Cross announces that a famine is striking Tajikistan, and calls for international financial aid for Tajikistan and Uzbekistan. |
| 94857 | August 21 | Event | 2013 – Hundreds of people are reported killed by chemical attacks in the Ghouta region of Syria. |
| 94858 | August 21 | Birth | 1165 – Philip II of France (d. 1223) |
| 94859 | August 21 | Birth | 1535 – Shimazu Yoshihiro, Japanese general (d. 1619) |
| 94860 | August 21 | Birth | 1567 – Francis de Sales, Swiss bishop and saint (d. 1622) |