- May 5 Hubert Howe Bancroft, American historian, ethnologist (History of Pacific States), born in Granville, Ohio (d. 1918)
- May 7 Carl Neumann, German mathematician and physicist (Neumann-functions), born in Königsberg, Prussia (d. 1925)
- May 14 Rudolf Lipschitz, German mathematician (d. 1903)
- May 16 Philip Danforth Armour, American industrialist (foundered meatpacking firm Armour Foods), born in Stockbridge, New York (d. 1901)
- May 21 Elizabeth Storrs Mead, American educator (d. 1917)
- May 23 Pieter Jan Baptist Carel Robidé van der Aa, Dutch Indologist and geographer, born in Oosterbeek, Netherlands (d. 1887)
- May 30 George Doherty Johnston, American Brigadier General (Confederate Army), born in Hillsborough, North Carolina (d. 1910)
20-29
30-39
40-49
50-59
80-89
Over 90