- May 3 Intercollegiate Athletic Association of the United States is renamed the National Collegiate Athletic Association (NCAA)
- May 4 Canadian Currency Act, 1910, receives Royal Assent
Historic Event
May 4 Wilfrid Laurier passes the Naval Service Act, which creates the Royal Canadian Navy
Nine Kings in One Room
May 6 George V becomes King of the United Kingdom upon the death of his father, Edward VII
- May 7 35th Preakness: R Estep aboard Layminster wins in 1:40.6
- May 10 1st aircraft air display held (Hendon, England)
- May 10 36th Kentucky Derby: Fred Herbert aboard Donau wins in 2:06.4
- May 10 Halley's Comet closest approach to Earth in 1910 pass
- May 10 The British House of Commons pass three major resolutions on political reform
- May 11 Montana's Glacier National Park forms
Conference of Interest
May 12 Second NAACP conference in NYC
- May 12 Philadelphia Athletics pitcher Charles "Chief" Bender no-hits Cleveland Naps, 4-0
- May 14 Canada authorizes issuing of silver dollar coins
- May 15 The last time a major earthquake happened on the Elsinore Fault Zone
- May 16 US Bureau of Mines forms
- May 17 Canada sets the designs for the 1-50 cent coins
- May 19 Passage of Earth through tail of Halley's Comet causes near-panic
Historic Event
May 20 Funeral for Britain's King Edward VII held in Westminster Abbey, has one of the largest assemblages of European royalty
Historic Event
May 21 Louis Botha becomes the first Prime Minister of the Union of South Africa
- May 27 Reform of Prussian three-class voting system fails
- May 29 Pope Pius X's encyclical on Editae Saepe, against church reformers
- May 30 44th Belmont: James Butwell aboard Sweep wins in 2:22
- May 31 Cape of Good Hope becomes part of Union of South Africa
- May 31 Glenn Curtiss flies from Albany to NYC
- May 31 Union of South Africa declares its independence from the United Kingdom