1955 – In the United States, a night-time F5tornado 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.
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.
1973 – , 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.
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).
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.