June 20 is the 171st day of the year (172nd in leap years) in the Gregorian calendar. 194 days remain until the end of the year.
In the Northern Hemisphere, the Summer solstice sometimes occurs on this date, while the Winter solstice occurs in the Southern Hemisphere.
- 451 – Battle of Chalons: Flavius Aetius' battles Attila the Hun. After the battle, which was inconclusive, Attila retreats, causing the Romans to interpret it as a victory.
- 1180 – First Battle of Uji, starting the Genpei War in Japan.
- 1620 – The Battle of Höchst takes place during the Thirty Years' War.
- 1631 – The Sack of Baltimore: The Irish village of Baltimore is attacked by Algerian pirates.
- 1652 – Tarhoncu Ahmed Pasha is appointed Grand Vizier of the Ottoman Empire.
- 1685 – Monmouth Rebellion: James Scott, 1st Duke of Monmouth declares himself King of England at Bridgwater.
- 1756 – A British garrison is imprisoned in the Black Hole of Calcutta.
- 1782 – The U.S. Congress adopts the Great Seal of the United States.
- 1787 – Oliver Ellsworth moves at the Federal Convention to call the government the 'United States'.
- 1789 – Deputies of the French Third Estate take the Tennis Court Oath.
- 1819 – The U.S. vessel SS Savannah arrives at Liverpool, United Kingdom. It is the first steam-propelled vessel to cross the Atlantic, although most of the journey is made under sail.
- 1837 – Queen Victoria succeeds to the British throne.
- 1840 – Samuel Morse receives the patent for the telegraph.
- 1862 – Barbu Catargiu, the Prime Minister of Romania, is assassinated.
- 1863 – American Civil War: West Virginia is admitted as the 35th U.S. state.
- 1877 – Alexander Graham Bell installs the world's first commercial telephone service in Hamilton, Ontario, Canada.
- 1893 – Lizzie Borden is acquitted of the murders of her father and stepmother.
- 1895 – The Kiel Canal, crossing the base of the Jutland peninsula and the busiest artificial waterway in the world, is officially opened.
- 1900 – Boxer Rebellion: The Imperial Chinese Army begins a 55-day siege of the Legation Quarter in Beijing, China.
- 1900 – Baron Eduard Toll, leader of the Russian Polar Expedition of 1900, departs Saint Petersburg in Russia on the explorer ship Zarya, never to return.
- 1921 – Workers of Buckingham and Carnatic Mills in the city of Chennai, India, begin a four-month strike.
- 1941 – The United States Army Air Corps is deprecated to being the American training and logistics section of what is known until 1947 as the United States Army Air Forces, just two days before Hitler's invasion of the Soviet Union.
- 1942 – The Holocaust: Kazimierz Piechowski and three others, dressed as members of the SS-Totenkopfverbände, steal an SS staff car and escape from the Auschwitz concentration camp.
- 1943 – The Detroit race riot breaks out and continues for three more days.
- 1943 – World War II: The Royal Air Force launches Operation Bellicose, the first shuttle bombing raid of the war. Lancaster bombers damage the V-2 rocket production facilities at the Zeppelin Works while en route to an air base in Algeria.
- 1944 – World War II: The Battle of the Philippine Sea concludes with a decisive U.S. naval victory. The lopsided naval air battle is also known as the "Great Marianas Turkey Shoot".
- 1944 – Continuation War: The Soviet Union demands an unconditional surrender from Finland during the beginning of partially successful Vyborg–Petrozavodsk Offensive. The Finnish government refuses.
- 1944 – The experimental MW 18014 V-2 rocket reaches an altitude of 176 km, becoming the first man-made object to reach outer space.
- 1945 – The United States Secretary of State approves the transfer of Wernher von Braun and his team of Nazi rocket scientists to the U.S. under Operation Paperclip.
- 1948 – The Deutsche Mark is introduced in Western Allied-occupied Germany. The Communists respond by imposing the Berlin Blockade four days later.
- 1956 – A Venezuelan Super-Constellation crashes in the Atlantic Ocean off Asbury Park, New Jersey, killing 74 people.
- 1959 – A rare June hurricane strikes Canada's Gulf of St. Lawrence killing 35.
- 1960 – The Mali Federation gains independence from France (it later splits into Mali and Senegal).
- 1963 – Following the Cuban Missile Crisis, the Soviet Union and the United States sign an agreement to establish the so-called "red telephone" link between Washington and Moscow.
- 1972 – Watergate scandal: An 18½-minute gap appears in the tape recording of the conversations between U.S. President Richard Nixon and his advisers regarding the recent arrests of his operatives while breaking into the Watergate complex.
- 1973 – Snipers fire upon left-wing Peronists in Buenos Aires, Argentina, in what is known as the Ezeiza massacre. At least 13 are killed and more than 300 are injured.
- 1973 – Aeroméxico Flight 229 crashes on approach to Licenciado Gustavo Díaz Ordaz International Airport, killing all 27 people on board.
- 1975 – The film Jaws is released in the United States, becoming the highest-grossing film of that time and starting the trend of films known as "summer blockbusters".
- 1979 – ABC News correspondent Bill Stewart is shot dead by a Nicaraguan soldier under the regime of Anastasio Somoza Debayle. The murder is caught on tape and sparks an international outcry against the regime.
- 1982 – The Argentine Corbeta Uruguay base on Southern Thule surrenders to Royal Marine commandos in the final action of the Falklands War.
- 1990 – Asteroid Eureka is discovered.
- 1990 – The 7.4 Mw Manjil–Rudbar earthquake affects northern Iran with a maximum Mercalli intensity of X (Extreme), killing 35,000–50,000, and injuring 60,000–105,000.
- 1991 – German Bundestag votes to move seat of government from the former West German capital of Bonn to the present capital Berlin.
- 1994 – The 1994 Imam Reza shrine bomb explosion in Iran leaves at least 25 dead and 70 to 300 injured.
- 2003 – The Wikimedia Foundation is founded in St. Petersburg, Florida.
srpskohrvatski / српскохрватски: 20. 6.