567 BC – Servius Tullius, the king of Rome, celebrates a triumph for his victory over the Etruscans.
240 BC – First recorded perihelion passage of Halley's Comet.
1085 – Alfonso VI of Castile takes Toledo, Spain, back from the Moors.
1420 – Henry the Navigator is appointed governor of the Order of Christ.
1521 – The Diet of Worms ends when Charles V, Holy Roman Emperor, issues the Edict of Worms, declaring Martin Luther an outlaw.
1644 – Ming general Wu Sangui forms an alliance with the invading Manchus and opens the gates of the Great Wall of China at Shanhaiguan pass, letting the Manchus through towards the capital Beijing.
1659 – Richard Cromwell resigns as Lord Protector of England following the restoration of the Long Parliament, beginning a second brief period of the republican government called the Commonwealth of England.
1738 – A treaty between Pennsylvania and Maryland ends the Conojocular War with settlement of a boundary dispute and exchange of prisoners.
1798 – United Irishmen Rebellion: Battle of Carlow begins; executions of suspected rebels at Carnew and at Dunlavin Green take place.
1809 – Chuquisaca Revolution: Patriot revolt in Chuquisaca (modern day Sucre) against the Spanish Empire, sparking the Latin American wars of independence.
1810 – May Revolution: citizens of Buenos Aires expel Viceroy Baltasar Hidalgo de Cisneros during the May week, starting the Argentine War of Independence.
1819 – The Argentine Constitution of 1819 is promulgated.
1833 – The Chilean Constitution of 1833 is promulgated.
1837 – The Rebels of Lower Canada (Quebec) rebel against the British for freedom.
1865 – In Mobile, Alabama, 300 are killed when an ordnance depot explodes.
1878 – Gilbert and Sullivan's comic opera H.M.S. Pinafore opens at the Opera Comique in London.
1895 – The playwright, poet, and novelist Oscar Wilde is convicted of "committing acts of gross indecency with other male persons" and sentenced to serve two years in prison.
1895 – The Republic of Formosa is formed, with Tang Ching-sung as its president.
1914 – The House of Commons of the United Kingdom passes the Home Rule Act for devolution in Ireland.
1925 – Scopes Trial: John T. Scopes is indicted for teaching Charles Darwin's theory of evolution in Tennessee.
1926 – Sholom Schwartzbard assassinates Symon Petliura, the head of the government of the Ukrainian People's Republic, which is in government-in-exile in Paris.
1935 – Jesse Owens of Ohio State University breaks three world records and ties a fourth at the Big Ten Conference Track and Field Championships in Ann Arbor, Michigan.
1936 – The Remington Rand strike, led by the American Federation of Labor, begins.
1938 – Spanish Civil War: The bombing of Alicante takes place, with 313 deaths.
1940 – World War II: The German 2nd Panzer Division captures the port of Boulogne-sur-Mer; the surrender of the last French and British troops marks the end of the Battle of Boulogne.
1946 – The parliament of Transjordan makes Abdullah I of Jordan their Emir.
1950 – Public transport: Green Hornet disaster. A Chicago Surface Lines streetcar crashes into a fuel truck, killing 33.
1953 – Nuclear testing: At the Nevada Test Site, the United States conduct their first and only nuclear artillery test.
1953 – The first public television station in the United States officially begins broadcasting as KUHT from the campus of the University of Houston.
1955 – In the United States, a night-time F5 tornado strikes the small city of Udall, Kansas, killing 80 and injuring 273. It is the deadliest tornado to ever occur in the state and the 23rd deadliest in the U.S.
1955 – First ascent of Kangchenjunga (8,586 m.), the third-highest mountain in the world, by a British expedition led by Charles Evans. Joe Brown and George Band reached the summit on May 25, followed by Norman Hardie and Tony Streather the next day.
1961 – Apollo program: U.S. President John F. Kennedy announces before a special joint session of the Congress his goal to initiate a project to put a "man on the Moon" before the end of the decade.
1961 – The Bukit Ho Swee Fire, the biggest fire in Singapore history.
1962 – The Old Bay Line, the last overnight steamboat service in the United States, goes out of business.
1963 – In Addis Ababa, Ethiopia, the Organisation of African Unity is established.
1966 – Explorer program: Explorer 32 launches.
1966 – The first prominent dàzìbào during the Cultural Revolution in China is posted at Peking University.
1967 – Celtic F.C. from Glasgow, Scotland, becomes the first ever Northern European team to win the European Cup; with previous winners being from Spain, Italy and Portugal.
1968 – Gateway Arch Saint Louis Gateway Arch is dedicated.
1973 – HNS Velos, while participating in a NATO exercise and in order to protest against the dictatorship in Greece, anchored at Fiumicino, Italy, refusing to return to Greece.
1977 – Star Wars is released in theaters.
1977 – Chinese government removes a decade old ban on William Shakespeare's work, effectively ending the Cultural Revolution started in 1966.
1979 – American Airlines Flight 191: In Chicago, a McDonnell Douglas DC-10 crashes during takeoff at O'Hare International Airport killing all 271 on board and two people on the ground.
1979 – Etan Patz, who is six years old, disappears from the street just two blocks away from his home in New York City, prompting an international search for the child, and causing the U.S. President Ronald Reagan to designate May 25 as National Missing Children's Day (in 1983).
1981 – In Riyadh, the Gulf Cooperation Council is created between Bahrain, Kuwait, Oman, Qatar, Saudi Arabia and the United Arab Emirates.
1982 – HMS Coventry is sunk during the Falklands War.
1985 – Bangladesh is hit by a tropical cyclone and storm surge, which kills approximately 10,000 people.
1986 – Hands Across America takes place.
1997 – A military coup in Sierra Leone replaces President Ahmad Tejan Kabbah with Major Johnny Paul Koromah.
1999 – The United States House of Representatives releases the Cox Report which details the People's Republic of China's nuclear espionage against the U.S. over the prior two decades.
2000 – Liberation Day of Lebanon. Israel withdraws its army from most of the Lebanese territory after 22 years of its first invasion in 1978.
2001 – Erik Weihenmayer, 32 years old, of Boulder, Colorado, becomes the first blind person to reach the summit of Mount Everest.
2002 – China Airlines Flight 611 disintegrates in mid-air and crashes into the Taiwan Strait. All 225 people on board are killed.
2008 – NASA's Phoenix lander lands in Green Valley region of Mars to search for environments suitable for water and microbial life.
2009 – North Korea allegedly tests its second nuclear device. Following the nuclear test, Pyongyang also conducted several missile tests building tensions in the international community.
2011 – Oprah Winfrey airs her last show, ending her twenty-five-year run of The Oprah Winfrey Show.
2012 – The Dragon became the first commercial spacecraft to successfully rendezvous with the International Space Station.
2013 – Suspected Maoist rebels kill at least 28 people and injure 32 others in an attack on a convoy of Indian National Congress politicians in Chhattisgarh, India.
2013 – A gas cylinder explodes on a school bus in the Pakistani city of Gujrat, killing at least 18 people.