May 21 is the 141st day of the year in the Gregorian calendar (142nd in leap years). There are 224 days remaining.

  1. 996 - Sixteen-year-old Otto III is crowned Holy Roman Emperor.
  2. 1502 - The island of Saint Helena is discovered by the Portuguese navigator João da Nova.
  3. 1674 - John Sobieski is elected by the szlachta to be the King of Poland.
  4. 1725 - The Order of Alexander Nevsky was instituted in Russia by an empress Catherine I.
  5. 1758 - Mary Campbell is abducted from her home in Pennsylvania by Lenape during the French and Indian War.
  6. 1851 - Abolition of slavery in Colombia, South America.
  7. 1856 - Lawrence, Kansas is captured and burned by pro-slavery forces.
  8. 1863 - American Civil War: Siege of Port Hudson – Union forces begin to lay siege to the Confederate-controlled Port Hudson, Louisiana.
  9. 1871 - French Government troops invade the Paris Commune and engage its residents in street fighting. By the close of "Bloody Week" some 20,000 communards have been killed and 38,000 arrested.
  10. 1879 - War of the Pacific: Two Chilean ships blocking the harbor of Iquique (then belonging to Peru), battle two Peruvian vessels in the Battle of Iquique.
  11. 1881 - The American Red Cross is established by Clara Barton.
  12. 1894 - The Manchester Ship Canal in England is officially opened by Queen Victoria, who knights its designer Sir Edward Leader Williams.
  13. 1894 - 22-year-old French Anarchist Emile Henry is executed by guillotine.
  14. 1904 - Fédération Internationale de Football Association (FIFA) founded in Paris.
  15. 1917 - Great Atlanta fire of 1917.
  16. 1924 - University of Chicago students Richard Loeb and Nathan Leopold, Jr. murder 14-year-old Bobby Franks in a "thrill killing."
  17. 1927 - Charles Lindbergh touchs down at Le Bourget Field in Paris, completing the world's first solo nonstop flight across the Atlantic Ocean.
  18. 1932 - Amelia Earhart, because of bad weather, lands in a pasture in Derry, Northern Ireland, becoming the first woman to fly solo across the Atlantic Ocean.
  19. 1934 - Oskaloosa, Iowa, becomes the first municipality in the United States to fingerprint each of its citizens.
  20. 1936 - Sada Abe is arrested after wandering the streets of Tokyo for days with her dead lover's severed genitals in her hand. Her story soon became one of Japan's most notorious scandals.
  21. 1937 - a Soviet station becomes the first scientific research settlement to operate on the drift ice of the Arctic Ocean.
  22. 1941 - World War II: 950 miles off the coast of Brazil, the freighter SS Robin Moor becomes the first United States ship sunk by a German U-boat.
  23. 1945 - United States screen legend Humphrey Bogart marries actress Lauren Bacall.
  24. 1951 - opening of the Ninth Street Show otherwise known as the 9th Street Art Exhibition was a gathering of a number of notable artists, and it was the stepping-out of the post war New York avant-garde, collectively know as the New York School.
  25. 1956 - Nuclear testing: In the Pacific Ocean, Bikini Atoll is nearly obliterated by the first airborne explosion of a hydrogen bomb.
  26. 1958 - United Kingdom Postmaster General Ernest Marples announces that from December, Subscriber Trunk Dialling will be introduced in the Bristol area.
  27. 1961 - American civil rights movement: Alabama Governor John Malcolm Patterson declares martial law in an attempt to restore order after race riots break out.
  28. 1972 - Michelangelo's Pietà, in St. Peter's Basilica in Rome, is damaged by a vandal.
  29. 1979 - White Night riots in San Francisco following the manslaughter conviction of Dan White for the assassinations of George Moscone and Harvey Milk.
  30. 1980 - Star Wars Episode V: The Empire Strikes Back opens in theaters.
  31. 1981 - Pierre Mauroy becomes Prime Minister of France.
  32. 1991 - Former Indian prime minister Rajiv Gandhi is assassinated by a female suicide bomber near Madras.
  33. 1996 - The MV Bukoba sinks in Tanzanian waters on Lake Victoria, killing nearly 1000.
  34. 1998 - At Thurston High School in Springfield, Oregon, Kipland Kinkel, suspended for bringing a gun to school, shoots a semi-automatic rifle into a room filled with students, killing 2 wounding 25 others after killing his parents at home.
  35. 1998 - Reproductive rights: In Miami, Florida, five abortion clinics are hit by a butyric acid attacker.
  36. 1998 - Soeharto, Indonesian dictator who had been ruling for 32 years, resigned.
  37. 2000 - A chartered British Aerospace Jetstream 31 crashes near Wilkes-Barre, Pennsylvania, killing 19.
  38. 2001 - French Taubira law which officially recognize the Atlantic slave trade and slavery as crimes against humanity.
  39. 2003 - An earthquake hits northern Algeria, killing more than 2,000 people.
  40. 2004 - Sherpa Pemba Dorje climbs Mount Everest in 8 hours 10 minutes, breaking his rival Sherpa Lakpa Gelu's record from the previous year.
  41. 2004 - Stanislav Petrov is awarded the World Citizen Award for averting a potential World War III in 1983.
  42. 2005 - In Kiev, Ukraine, Greece wins the fiftieth Eurovision Song Contest with "My Number One" performed by Elena Paparizou.
  43. 2006 - The Republic of Montenegro holds a referendum proposing independence from the State Union of Serbia and Montenegro.
  44. 2006 - The Swedish ice hockey team Tre Kronor takes gold in the World Championship and becomes the first nation to take gold in both the World Championship and Olympic games in ice hockey.