* 585 BC – A solar eclipse occurs, as predicted by Greek philosopher and scientist Thales, while Alyattes is battling Cyaxares in the Battle of the Eclipse, leading to a truce. This is one of the cardinal dates from which other dates can be calculated.
* 1503 – James IV of Scotland and Margaret Tudor are married according to a Papal Bull by Pope Alexander VI. A Treaty of Everlasting Peace between Scotland and England signed on that occasion results in a peace that lasts ten years.
* 1533 – The Archbishop of Canterbury Thomas Cranmer declares the marriage of King Henry VIII of England to Anne Boleyn valid.
* 1588 – The Spanish Armada, with 130 ships and 30,000 men, sets sail from Lisbon heading for the English Channel. (It will take until May 30 for all ships to leave port).
* 1644 – Bolton Massacre by Royalist troops under the command of the Earl of Derby.
* 1754 – French and Indian War: in the first engagement of the war, Virginia militia under 22-year-old Lieutenant Colonel George Washington defeat a French reconnaissance party in the Battle of Jumonville Glen in what is now Fayette County in southwestern Pennsylvania.
* 1774 – American Revolutionary War: the first Continental Congress convenes.
* 1830 – President Andrew Jackson signs the Indian Removal Act which relocates Native Americans.
* 1859 – Big Ben is drawn on a carriage pulled by 16 horses from Whitechapel Bell Foundry to the Palace of Westminster.
* 1863 – American Civil War: The 54th Massachusetts Volunteer Infantry, the first African American regiment, leaves Boston, Massachusetts, to fight for the Union.
* 1892 – In San Francisco, California, John Muir organizes the Sierra Club.
* 1905 – Russo-Japanese War: The Battle of Tsushima ends with the destruction of the Russian Baltic Fleet by Admiral Togo Heihachiro and the Imperial Japanese Navy.
* 1918 – The Azerbaijan Democratic Republic and the Democratic Republic of Armenia declare their independence.
* 1926 – 28th May 1926 coup d'état: Ditadura Nacional is established in Portugal to suppress the unrest of the First Republic.
* 1930 – The Chrysler Building in New York City officially opens.
* 1934 – Near Callander, Ontario, the Dionne quintuplets are born to Oliva and Elzire Dionne; they will be the first quintuplets to survive infancy.
* 1934 – The Glyndebourne festival in England is inaugurated.
* 1936 – Alan Turing submits On Computable Numbers for publication.
* 1937 – The Golden Gate Bridge in San Francisco, California, is officially opened by President Franklin D. Roosevelt in Washington, D.C., who pushes a button signaling the start of vehicle traffic over the span.
* 1937 – Neville Chamberlain becomes British Prime Minister.
* 1940 – World War II: Belgium surrenders to Germany.
* 1940 – World War II: Norwegian, French, Polish and British forces recapture Narvik in Norway. This is the first allied infantry victory of the War.
* 1942 – World War II: in retaliation for the assassination of Reinhard Heydrich, Nazis in Czechoslovakia kill over 1,800 people.
* 1952 – Memphis Kiddie Park opens in Brooklyn, Ohio. The park's Little Dipper roller coaster would become the oldest operating steel roller coaster in North America.
* 1952 – The women of Greece are given the right to vote.
* 1955 – Henry Bolte becomes Premier of the state of Victoria.
* 1961 – Peter Benenson's article The Forgotten Prisoners is published in several internationally read newspapers. This will later be thought of as the founding of the human rights organization Amnesty International.
* 1964 – The Palestine Liberation Organization is formed.
* 1970 – The formerly united Free University of Brussels officially splits into two separate entities, the French-speaking Université Libre de Bruxelles and the Dutch-speaking Vrije Universiteit Brussel.
* 1974 – Northern Ireland's power-sharing Sunningdale Agreement collapses following a general strike by loyalists.
* 1975 – Fifteen West African countries sign the Treaty of Lagos, creating the Economic Community of West African States.
* 1977 – In Southgate, Kentucky, the Beverly Hills Supper Club is engulfed in fire, killing 165 people inside.
* 1978 – Second round of the presidential elections in Upper Volta. The election is won by incumbent Sangoulé Lamizana.
* 1979 – Constantine Karamanlis signs the full treaty of the accession of Greece with the European Economic Community.
* 1982 – Falklands War: British forces defeat the Argentines at the Battle of Goose Green.
* 1987 – 19-year-old West German pilot Mathias Rust evades Soviet Union air defenses and lands a private plane in the Red Square in Moscow. He is immediately detained and will not be released until August 3, 1988.
* 1987 – A robot probe finds the wreckage of the USS Monitor near Cape Hatteras, North Carolina.
* 1991 – The capital city of Addis Ababa, falls to the Ethiopian People's Revolutionary Democratic Front, ending both the Derg regime in Ethiopia and the Ethiopian Civil War.
* 1993 – Eritrea and Monaco join the United Nations.
* 1995 – The Russian town of Neftegorsk is hit by a 7.6 magnitude earthquake that kills at least 2,000 people, half of the total population.
* 1996 – U.S. President Bill Clinton's former business partners in the Whitewater land deal, James McDougal and Susan McDougal, and the Governor of Arkansas Jim Guy Tucker, are convicted of fraud.
* 1998 – Nuclear testing: Pakistan responds to a series of nuclear tests by India with five of its own, prompting the United States, Japan, and other nations to impose economic sanctions.
* 1999 – In Milan, Italy, after 22 years of restoration work, Leonardo da Vinci's masterpiece The Last Supper is put back on display.
* 1999 – Two Swedish police officers are murdered with their own fire arms by the bank robbers Jackie Arklöv and Tony Olsson after a car chase.
* 2002 – NATO declares Russia a limited partner in the Western alliance.
* 2002 – The Mars Odyssey finds signs of large ice deposits on the planet Mars.
* 2003 – Peter Hollingworth becomes the first Governor-General of Australia to resign his office as a result of criticism of his conduct.
* 2004 – The Iraqi Governing Council chooses Ayad Allawi, a longtime anti-Saddam Hussein exile, as prime minister of Iraq's interim government.
* 2008 – The first meeting of the Constituent Assembly of Nepal formally declares Nepal a republic, ending the 240-year reign of the Shah dynasty.