August 20

• 917 - Battle of Anchialus: Tsar Simeon I of Bulgaria invades Thrace and drives the Byzantines out.
• 1794 - Battle of Fallen Timbers - American troops force a confederacy of Shawnee, Mingo, Delaware, Wyandot, Miami, Ottawa, Chippewa and Potawatomi warriors into a disorganized retreat.
• 1804 - Lewis and Clark Expedition: The "Corps of Discovery", whose purpose is to explore the Louisiana Purchase, suffers it first and last death when Sergeant Charles Floyd dies, apparently from acute appendicitis.
• 1882 - Piotr Ilyitch Tchaikovsky's "1812 Overture" debuts in Moscow.
• 1914 - World War I: German forces occupy Brussels.
• 1920 - The first commercial radio station, 8MK (WWJ), begins operations in Detroit, Michigan.
• 1940 - Exiled Russian revolutionary Leon Trotsky is fatally wounded in Mexico City by an assassin's ice-ax. He will die the next day.
• 1955 - In Morocco, a force of Berbers from the Atlas Mountains region of Algeria, raid two rural settlements and kill 77 French nationals.
• 1960 - Senegal breaks from the Mali federation, declaring independence.
• 1968 - 200,000 Warsaw Pact troops and 5,000 tanks invade Czechoslovakia to end the "Prague Spring" of political liberalization.
• 1975 - Viking program: NASA launches the Viking 1 planetary probe toward Mars.
• 1977 - Voyager program: The United States launches the Voyager 2 spacecraft.
• 1982 - Lebanese Civil War: A multinational force lands in Beirut to oversee the PLO withdrawal from Lebanon.
• 1986 - In Edmond, Oklahoma, US Postal employee Patrick Henry Sherrill guns down 14 of his co-workers and then commits suicide.
• 1989- In Beverly Hills, California, Lyle and Erik Menendez shoot their wealthy parents to death in their family's den.
• 1991 - Collapse of the Soviet Union: Estonia declares its independence from the Soviet Union.
• 1991 - Collapse of the Soviet Union: More than 100,000 people rally outside the Soviet Union's parliament building protesting the coup that deposed President Mikhail Gorbachev.
• 1998 - The Supreme Court of Canada states Quebec can not legally secede from Canada without the federal government's approval.
• 1998 - 1998 U.S. embassy bombings: The United States military launches cruise missile attacks against alleged al-Quaida camps in Afghanistan and a suspected chemical plant in Sudan in retaliation for the August 7 bombings of American embassies in Kenya and Tanzania. The al-Shifa pharmaceutical factory in Khartoum is destroyed in the attack.

• 1561 - Jacopo Peri, composer
• 1779 - Jons Jacob Berzelius, chemist
• 1833 - Benjamin Harrison, 23rd President of the United States
• 1881 - Edgar Guest, poet
• 1890 - H. P. Lovecraft, horror writer (d. 1937)
• 1905 - Jack Teagarden, jazz musician (d. 1964)
• 1910 - Eero Saarinen, architect
• 1918 - Jacqueline Susann, novelist (d. 1974)
• 1923 - Jim Reeves, country and western singer (d. 1964)
• 1931 - Don King, boxing promoter
• 1941 - Slobodan Milosevic, former president of Serbia and Yugoslabia
• 1942 - Isaac Hayes, singer, songwriter, actor
• 1944 - Rajiv Gandhi, Prime Minister of India (d. 1991)
• 1946 - Connie Chung, journalist
• 1948 - Robert Plant, rock and roll singer
• 1949 - Phil Lynott, rock and roll musician (d. 1986)
• 1951 - Greg Bear, science fiction author
• 1952 - John Hiatt, musician
• 1954 - Al Roker, television broadcaster
• 1955 - Agnes Chan, singer, professor of education, essayist
• 1956 - Joan Allen, actress (Nixon, Pleasantville)
• 1965 - KRS-One (Lawrence Krisna Parker), rap music singer
• 1968 - Shiratori Yuri, seiyuu

• 984 - Pope John XIV
• 1611 - Tomás Luis de Victoria, composer
• 1823 - Pope Pius VII
• 1914 - Pope Pius X
• 1940 - Leon Trotsky, Bolshevik revolutionary
• 2001 - Sir Fred Hoyle, astronomer, science fiction writer

• Bahá'í Faith - Feast of Asmá (Names) - First day of the ninth month of the Bahá'í Calendar
• St. Stephen's day in Hungary, the main national holiday