Wikipedia:Selected anniversaries/June 20
June 20: Father's Day in Bulgaria (2024), Flag Day in Argentina (since 1938)
- 451 - The Battle of Chalons against Attila the Hun is the last major battle of the Western Roman Empire.
- 1756 - A garrison of the British army in India was imprisoned in the Black Hole of Calcutta.
- 1789 - 577 deputies of the French National Assembly took the Tennis Court Oath, starting the French Revolution.
- 1837 - Queen Victoria (pictured) succeeded to the British throne.
- 1947 - A Mafia hitman murdered gangster Bugsy Siegel in Beverly Hills, California, United States.