June 20: World Refugee Day; Flag Day in Argentina
- 451 – A coalition led by Roman General Flavius Aetius and Visigothic king Theodoric I clashed violently with the Hunnic alliance commanded by Attila at the Battle of the Catalaunian Plains.
- 1819 – Arriving in Liverpool, the SS Savannah (pictured) became the first steamship to cross the Atlantic Ocean.
- 1862 – Barbu Catargiu, the first Prime Minister of Romania, was assassinated after denying people the right of assembly to commemorate the Revolutions of 1848.
- 1893 – After a widely publicized trial, American Lizzie Borden was acquitted of the murder of her father and stepmother.
- 1900 – Boxer Rebellion: The Imperial Chinese Army began a 55-day siege of the Legation Quarter in Beijing.
- 1973 – Snipers fired into a crowd of Peronists near the Ezeiza Airport in Buenos Aires, killing at least 13 people and injuring 365 others.