325 – The First Council of Nicaea is formally opened, starting the first ecumenical council of the Christian Church.
491 – Empress Ariadne marries Anastasius I. The widowed Augusta is able to choose her successor for the Byzantine throne, after Zeno (late emperor) dies of dysentery.
685 – The Battle of Dun Nechtain is fought between a Pictish army under King Bridei III and the invading Northumbrians under King Ecgfrith, who are decisively defeated.
794 – While visiting the royal Mercian court at Sutton Walls with a view to marrying princess Ælfthryth, King Æthelberht II of East Anglia is taken captive and beheaded.
1217 – The Second Battle of Lincoln is fought near Lincoln, England, resulting in the defeat of Prince Louis of France by William Marshal, 1st Earl of Pembroke.
1293 – King Sancho IV of Castile creates the Estudio de Escuelas de Generales in Alcalá de Henares.
1449 – The Battle of Alfarrobeira is fought, establishing the House of Braganza as a principal royal family of Portugal.
1497 – John Cabot sets sail from Bristol, England, on his ship Matthew looking for a route to the west (other documents give a May 2 date).
1498 – Portuguese explorer Vasco da Gama discovers the sea route to India when he arrives at Kozhikode (previously known as Calicut), India.
1521 – Ignatius of Loyola is seriously wounded in the Battle of Pampeluna.
1570 – Cartographer Abraham Ortelius issues Theatrum Orbis Terrarum, the first modern atlas.
1609 – Shakespeare’s sonnets are first published in London, perhaps illicitly, by the publisher Thomas Thorpe.
1631 – The city of Magdeburg in Germany is seized by forces of the Holy Roman Empire and most of its inhabitants massacred, in one of the bloodiest incidents of the Thirty Years’ War.
1645 – Yangzhou massacre: The ten day massacre of 800,000 residents of the city of Yangzhou, part of the Transition from Ming to Qing.
1741 – The Battle of Cartagena de Indias ends in a Spanish victory and the British begin withdrawal towards Jamaica with substantial losses.
1775 – The Mecklenburg Declaration of Independence is allegedly signed in Charlotte, North Carolina.
1802 – By the Law of 20 May 1802, Napoleon Bonaparte reinstates slavery in the French colonies, revoking its abolition in the French Revolution.
1813 – Napoleon Bonaparte leads his French troops into the Battle of Bautzen in Saxony, Germany, against the combined armies of Russia and Prussia. The battle ends the next day with a French victory.
1840 – York Minster is badly damaged by fire.
1861 – American Civil War: The state of Kentucky proclaims its neutrality, which will last until September 3 when Confederate forces enter the state. Meanwhile, the State of North Carolina secedes from the Union.
1862 – U.S. President Abraham Lincoln signs the Homestead Act into law, opening 84 million acres of public land to settlers.
1864 – American Civil War: Battle of Ware Bottom Church: In the Virginia Bermuda Hundred campaign, 10,000 troops fight in this Confederate victory.
1873 – Levi Strauss and Jacob Davis receive a U.S. patent for blue jeans with copper rivets.
1875 – Signing of the Metre Convention by 17 nations leading to the establishment of the International System of Units.
1882 – The Triple Alliance between the German Empire, Austria-Hungary and the Kingdom of Italy is formed.
1883 – Krakatoa begins to erupt; the volcano explodes three months later, killing more than 36,000 people.
1891 – History of cinema: The first public display of Thomas Edison’s prototype kinetoscope.
1902 – Cuba gains independence from the United States. Tomás Estrada Palma becomes the country’s first President.
1927 – Treaty of Jeddah: The United Kingdom recognizes the sovereignty of King Ibn Saud in the Kingdoms of Hejaz and Nejd, which later merge to become the Kingdom of Saudi Arabia.
1932 – Amelia Earhart takes off from Newfoundland to begin the world’s first solo nonstop flight across the Atlantic Ocean by a female pilot, landing in Ireland the next day.
1940 – The Holocaust: The first prisoners arrive at a new concentration camp at Auschwitz.
1941 – World War II: Battle of Crete: German paratroops invade Crete.
1948 – Generalissimo Chiang Kai-shek wins the 1948 Republic of China presidential election and is sworn in as the first President of the Republic of China at Nanjing.
1949 – In the United States, the Armed Forces Security Agency, the predecessor to the National Security Agency, is established.
1956 – In Operation Redwing, the first United States airborne hydrogen bomb is dropped over Bikini Atoll in the Pacific Ocean.
1964 – Discovery of the cosmic microwave background radiation by Robert Woodrow Wilson and Arno Penzias.
1967 – The Popular Movement of the Revolution political party is established in the Democratic Republic of the Congo.
1969 – The Battle of Hamburger Hill in Vietnam ends.
1971 – In the Chuknagar massacre, Pakistani forces massacre thousands, mostly Bengali Hindus.
1980 – In a referendum in Quebec, the population rejects, by 60% of the vote, a government proposal to move towards independence from Canada.
1983 – First publications of the discovery of the HIV virus that causes AIDS in the journal Science by Luc Montagnier.
1983 – Church Street bombing: A car bomb planted by Umkhonto we Sizwe explodes on Church Street in South Africa’s capital, Pretoria, killing 19 people and injuring 217 others.
1985 – Radio Martí, part of the Voice of America service, begins broadcasting to Cuba.
1989 – The Chinese authorities declare martial law in the face of pro-democracy demonstrations, setting the scene for the Tiananmen Square massacre.
1990 – The first post-Communist presidential and parliamentary elections are held in Romania.
1996 – Civil rights: The Supreme Court of the United States rules in Romer v. Evans against a law that would have prevented any city, town or county in the state of Colorado from taking any legislative, executive, or judicial action to protect the rights of gays and lesbians.
2002 – The independence of East Timor is recognized by Portugal, formally ending 23 years of Indonesian rule and three years of provisional UN administration (Portugal itself is the former colonizer of East Timor until 1976).
2012 – At least 27 people are killed and 50 others injured when a 6.0-magnitude earthquake strikes northern Italy.
2013 – An EF5 tornado strikes the Oklahoma City suburb of Moore, killing 24 people and injuring 377 others.
2019 – The International System of Units (SI): The base units are redefined, making the international prototype of the kilogram obsolete.
Births on May 20
1315 – Bonne of Luxembourg, first wife of John II of France (d. 1349)
1470 – Pietro Bembo, Italian cardinal, poet, and scholar (d. 1547)
1505 – Levinus Lemnius, Dutch writer (d. 1568)
1531 – Thado Minsaw of Ava, Viceroy of Ava (d. 1584)
1537 – Hieronymus Fabricius, Italian anatomist (d. 1619)
1575 – Robert Heath, English judge and politician (d. 1649)
1664 – Andreas Schlüter, German sculptor and architect (d. 1714)
1726 – Francis Cotes, English painter and academic (d. 1770)
1743 – Toussaint Louverture, Haitian revolutionary, general, and president (d. 1803)
1759 – William Thornton, Virgin Islander-American architect, designed the United States Capitol (d. 1828)
1769 – Andreas Vokos Miaoulis, Greek admiral and politician (d. 1835)
1772 – Sir William Congreve, 2nd Baronet, English inventor and politician, developed Congreve rockets (d. 1828)
1776 – Simon Fraser, American-Canadian fur trader and explorer (d. 1862)
1795 – Pedro María de Anaya, Mexican soldier. President (1847-1848) (d. 1854)
1799 – Honoré de Balzac, French novelist and playwright (d. 1850)
1806 – John Stuart Mill, English economist, civil servant, and philosopher (d. 1873)
1811 – Alfred Domett, English-New Zealand poet and politician, 4th Prime Minister of New Zealand (d. 1887)
1818 – William Fargo, American businessman and politician, co-founded Wells Fargo and American Express (d. 1881)
1822 – Frédéric Passy, French economist and academic, Nobel Prize laureate (d. 1912)
1824 – Cadmus M. Wilcox, Confederate States Army general (d. 1890)
1825 – Antoinette Brown Blackwell, the first woman to be ordained as a mainstream Protestant minister in the U.S. (d. 1921)
1830 – Hector Malot, French author (d. 1907)
1838 – Jules Méline, French lawyer and politician, 65th Prime Minister of France (d. 1925)
1851 – Emile Berliner, German-American inventor, invented the Gramophone record (d. 1929)
1854 – George Prendergast, Australian politician, 28th Premier of Victoria (d. 1937)
1856 – Henri-Edmond Cross, French Neo-Impressionist painter (d. 1910)
1860 – Eduard Buchner, German chemist, zymologist, and academic, Nobel Prize laureate (d. 1917)
1875 – Hendrik Offerhaus, Dutch rower (d. 1953)
1877 – Pat Leahy, Irish-American jumper (d. 1927)
1879 – Hans Meerwein, German chemist (d. 1965)
1882 – Sigrid Undset, Danish-Norwegian novelist, essayist, and translator, Nobel Prize laureate (d. 1949)
1883 – Faisal I of Iraq (d. 1933)
1886 – Ali Sami Yen, Turkish footballer and manager, founded the Galatasaray Sports Club (d. 1951)
1894 – Chandrashekarendra Saraswati, Indian guru and scholar (d. 1994)
1895 – R. J. Mitchell, English engineer, designed the Supermarine Spitfire and Supermarine S.6B (d. 1937)
1897 – Diego Abad de Santillán, Spanish economist and author (d. 1983)
1897 – Malcolm Nokes, English hammer and discus thrower (d. 1986)
1898 – Eduard Ole, Estonian painter (d. 1995)
1899 – Aleksandr Deyneka, Russian painter and sculptor (d. 1969)
1899 – John Marshall Harlan II, American lawyer and jurist (d. 1971)
1900 – Sumitranandan Pant, Indian poet and author (d. 1977)
1901 – Max Euwe, Dutch chess player, mathematician, and author (d. 1981)
1901 – Doris Fleeson, American journalist (d. 1970)
1904 – Margery Allingham, English author of detective fiction (d. 1966)
1906 – Giuseppe Siri, Italian cardinal (d. 1989)
1907 – Carl Mydans, American photographer and journalist (d. 2004)
1908 – Henry Bolte, Australian politician, 38th Premier of Victoria (d. 1990)
1908 – Louis Daquin, French actor and director (d. 1980)
1908 – Francis Raymond Fosberg, American botanist and author (d. 1993)
1908 – James Stewart, American actor (d. 1997)
1911 – Gardner Fox, American author (d. 1986)
1911 – Annie M. G. Schmidt, Dutch author and playwright (d. 1995)
1913 – Teodoro Fernández, Peruvian footballer (d. 1996)
1913 – William Redington Hewlett, American engineer, co-founded Hewlett-Packard (d. 2001)
1915 – Peter Copley, English actor (d. 2008)
1915 – Moshe Dayan, Israeli general and politician, 5th Israeli Minister of Foreign Affairs (d. 1981)
1915 – Joff Ellen, Australian comedian and actor (d. 1999)
1916 – Owen Chadwick, English rugby player, historian, and academic (d. 2015)
1916 – Alexey Maresyev, Russian soldier and pilot (d. 2001)
1916 – Ondina Valla, Italian sprinter and hurdler (d. 2006)
1917 – Tony Cliff, Israeli-English author and activist (d. 2000)
1917 – Guy Favreau, Canadian lawyer, judge, and politician, 28th Canadian Minister of Justice (d. 1967)
1918 – Alexandra Boyko, Russian tank commander (d. 1996)
1918 – Edward B. Lewis, American biologist, geneticist, and academic, Nobel Prize laureate (d. 2004)
1919 – George Gobel, American comedian (d. 1991)
1920 – John Cruickshank, Scottish lieutenant and banker, Victoria Cross recipient
1921 – Wolfgang Borchert, German author and playwright (d. 1947)
1921 – Hal Newhouser, American baseball player and scout (d. 1998)
1921 – Hao Wang, Chinese-American logician, philosopher, and mathematician (d. 1995)
1922 – Ted Hinton, Northern Irish international footballer (d. 1988)
1923 – Edith Fellows, American actress (d. 2011)
1923 – Sam Selvon, Trinidad-born writer (d. 1994)
1924 – David Chavchavadze, English-American CIA officer and author (d. 2014)
1924 – Zelmar Michelini, Uruguayan journalist and politician (d. 1976)
1925 – Alexei Tupolev, Russian engineer, designed the Tupolev Tu-144 (d. 2001)
1926 – Bob Sweikert, American race car driver (d. 1956)
1927 – Bud Grant, American football player and coach
1927 – David Hedison, American actor (d. 2019)
1927 – Franciszek Macharski, Polish cardinal (d. 2016)
1929 – Gilles Loiselle, Canadian politician and diplomat, 33rd Canadian Minister of Finance
1930 – Sam Etcheverry, American football player and coach (d. 2009)
1931 – Ken Boyer, American baseball player and manager (d. 1982)
1931 – Louis Smith, American trumpeter (d. 2016)
1933 – Constance Towers, American actress and singer
1935 – José Mujica, Uruguayan guerrilla leader and politician, 40th President of Uruguay
1936 – Anthony Zerbe, American actor
1937 – Dave Hill, American golfer (d. 2011)
1937 – Derek Lampe, English footballer
1939 – Balu Mahendra, Sri Lankan-Indian director, cinematographer, and screenwriter (d. 2014)
1940 – Shorty Long, American singer-songwriter and producer (d. 1969)
1940 – Stan Mikita, Slovak-Canadian ice hockey player and sportscaster (d. 2018)
1940 – Sadaharu Oh, Japanese-Taiwanese baseball player and manager
1941 – Goh Chok Tong, Singaporean politician, 2nd Prime Minister of Singapore
1941 – John Strasberg, American actor and teacher
1942 – Raymond Chrétien, Canadian lawyer and diplomat, Canadian Ambassador to the United States
1942 – Lynn Davies, Welsh sprinter and long jumper
1942 – Carlos Hathcock, American sergeant and sniper (d. 1999)
1942 – Frew McMillan, South African tennis player
1943 – Albano Carrisi, Italian singer, actor, and winemaker
1943 – Deryck Murray, Trinidadian cricketer
1944 – Joe Cocker, English singer-songwriter (d. 2014)
1944 – Boudewijn de Groot, Indonesian-Dutch singer-songwriter and guitarist
1944 – Keith Fletcher, English cricketer and manager
1944 – Dietrich Mateschitz, Austrian businessman, co-founded Red Bull GmbH
