May 15 is the 135th day of the year in the Gregorian Calendar (136th in leap years). There are 230 days remaining.

  1. 1252 - Pope Innocent IV issues the papal bull ad exstirpanda, which authorizes the torture of heretics in the Medieval Inquisition. Torture quickly gains widespread usage across Catholic Europe.
  2. 1514 - Jodocus Badius Ascensius publishes Christiern Pedersen's Latin version of Saxo’s Gesta Danorum, the oldest known version of that work.
  3. 1525 - The battle of Frankenhausen ends the Peasants' War.
  4. 1567 - Mary Queen of Scots weds James Hepburn, Earl of Bothwell, her third husband.
  5. 1602 - Bartholomew Gosnold becomes the first European to see Cape Cod.
  6. 1618 - Johannes Kepler confirms his previously rejected discovery of the third law of planetary motion (he first discovered it on March 8 but soon rejected the idea after some initial calculations were made).
  7. 1701 - The War of the Spanish Succession begins.
  8. 1718 - James Puckle, a London lawyer, patents the world's first machine gun.
  9. 1756 - The Seven Years' War begins when England declares war on France.
  10. 1776 - American Revolution: Virginia convention instructs its delegates to propose a declaration of independence from Great Britain.
  11. 1791 - Maximilien Robespierre proposed the self-denying ordinance.
  12. 1795 - First Coalition: Napoleon I of France enters Milan in triumph.
  13. 1811 - Paraguay declares independence from Spain.
  14. 1829 - According to LDS teaching, John the Baptist confers the Aaronic Priesthood onto Joseph Smith Jr. and Oliver Cowdery.
  15. 1836 - Francis Baily observes "Baily's beads" during an annular eclipse.
  16. 1849 - Troops of the Two Sicilies take Palermo and crush the republican government of Sicily.
  17. 1851 - Rama IV is crowned King of Thailand.
  18. 1858 - The third Royal Opera House officially opens in London.
  19. 1862 - President Abraham Lincoln signs a bill into law creating the United States Bureau of Agriculture (later renamed USDA).
  20. 1864 - American Civil War: Battle of Resaca, Georgia ends.
  21. 1864 - American Civil War: Battle of New Market, Virginia – Students from the Virginia Military Institute fight alongside the Confederate Army to force Union General Franz Sigel out of the Shenandoah Valley.
  22. 1869 - Woman's suffrage: In New York, Susan B. Anthony and Elizabeth Cady Stanton form the National Woman Suffrage Association.
  23. 1897 - The Greek army retreats with heavy losses in Greco-Turkish War
  24. 1902 - In a field outside Grass Valley, California, Lyman Gilmore reportedly becomes the first person to fly a powered airplane (a steam-powered glider).
  25. 1905 - Las Vegas, Nevada, is founded when 110 acres (0.4 km²), in what later would become downtown, are auctioned off.
  26. 1910 - The last time a major earthquake happened on the Lake Elsinore Fault.
  27. 1911 - The United States Supreme Court declares Standard Oil to be an "unreasonable" monopoly under the Sherman Antitrust Act and orders the company to be dissolved.
  28. 1914 - Bolivia becomes a signatory to the Buenos Aires copyright treaty.
  29. 1918 - Finnish Civil War ends.
  30. 1918 - The US Post Office Department (later renamed the USPS) begins the first regular airmail service in the world (between New York City, Philadelphia and Washington, DC).
  31. 1919 - The Winnipeg General Strike began. By 11:00, virtually the entire working population of Winnipeg had walked off the job.
  32. 1919 - Greek invasion of Izmir, resulting in the massacre of hundreds of Turks by the Greek army. Hasan Tahsin fired the first gun of the Turkish War of Independence.
  33. 1920 - Council of Lithuania adjourned as newly elected Constituent Assembly of Lithuania met for the first time in Kaunas
  34. 1928 - Release of the animated short "Plane Crazy", featuring the first appearances of Mickey and Minnie Mouse.
  35. 1929 - A fire at the Cleveland Clinic in Cleveland, Ohio kills 123.
  36. 1930 - Aboard a Boeing tri-motor, Ellen Church becomes the first airline stewardess, on a flight from Oakland, California to Chicago.
  37. 1932 - The May 15 Incident. In an attempted coup the Prime Minister of Japan Inukai Tsuyoshi is killed.
  38. 1934 - The United States Department of Justice offers a $25,000 reward for John Dillinger.
  39. 1934 - Karlis Ulmanis establishes an authoritarian government in Latvia.
  40. 1940 - Nylon stockings go on sale for the first time in the United States.
  41. 1940 - World War II: After fierce fighting, the poorly trained and equipped Dutch troops have to surrender to Nazi Germany, marking the beginning of 5 years of occupation.
  42. 1940 - McDonald's is founded.
  43. 1941 - Baseball player Joe DiMaggio starts his record-breaking 56-game hitting streak.
  44. 1942 - World War II: In the United States, a bill creating the Women's Auxiliary Army Corps (WAAC) is signed into law.
  45. 1943 - Joseph Stalin dissolves the Comintern (or Third International).
  46. 1945 - Last skirmish of the Second World War in Europe fought near Prevalje, Slovenia.
  47. 1948 - Egypt, Transjordan, Lebanon, Syria, Iraq and Saudi Arabia attack Israel.
  48. 1951 - The Polish cultural attache in Paris, Czeslaw Milosz, asks the French government for political asylum.
  49. 1951 - The cartoon Rabbit Fire is released
  50. 1955 - Austrian Independence Treaty signed.
  51. 1955 - First ascent of Makalu, the world's fifth highest mountain.
  52. 1957 - Britain tests its first hydrogen bomb in Operation Grapple.
  53. 1958 - The Soviet Union launches Sputnik 3.
  54. 1960 - The Soviet Union launches Sputnik 4.
  55. 1963 - Mercury program: America launches the last mission of the program, Mercury 9 (on June 12 NASA Administrator James E. Webb told Congress the program was complete).
  56. 1964 - The Smothers Brothers give their first concert in Carnegie Hall in New York City.
  57. 1970 - The Beatles' last LP, Let It Be, is released in the United States.
  58. 1970 - President Richard Nixon appoints Anna Mae Hays and Elizabeth P. Hoisington the first female United States Army Generals.
  59. 1970 - Philip Lafayette Gibbs and James Earl Green killed at Jackson State University by police during student protests.
  60. 1972 - The island of Okinawa, under U.S. military governance since its conquest in 1945, reverts to Japanese control.
  61. 1972 - In Laurel, Maryland, Arthur Bremer shoots and paralyzes Alabama Governor George Wallace while Wallace is campaigning to be American President.
  62. 1978 - Lagumot Harris, having only been elected President less than a month before, is replaced as the leader of the republic of Nauru. He is succeeded by Hammer DeRoburt.
  63. 1981 - Len Barker, American baseball pitcher, completes a perfect game for the Cleveland Indians against the Toronto Blue Jays.
  64. 1987 - Soviet Union launches the Polyus prototype orbital weapons platform, which failed to reach orbit.
  65. 1988 - Soviet war in Afghanistan: After more than eight years of fighting, the Red Army begins its withdrawal from Afghanistan.
  66. 1990 - Portrait of Doctor Gachet by Vincent van Gogh is sold for a record $82.5 million, the most expensive painting at the time.
  67. 1991 - Edith Cresson becomes France's first female prime minister.
  68. 2004 - The largest known prime number at the time of its discovery, 224036583 - 1, is found by Josh Findley and the GIMPS collaborative effort.
  69. 2004 - Arsenal complete a whole English Premiership season, 38 games, unbeaten.