- May 8 William Walker, American physician and president of Nicaragua (1856-57), born in Nashville, Tennessee (d. 1860)
- May 9 William Edmonson "Grumble" Jones, American Brigadier General (Confederate Army), born in Washington County, Virginia (d. 1864)
- May 10 Charles Henry Van Wyck, American politician and Brigadier General (Union Army), born in Poughkeepsie, New York (d. 1895)
- May 11 Jean-Léon Gérôme, French painter and sculptor, born in Rome, Italy (d. 1904)
- May 16 Edmund Kirby Smith, American General (Confederate Army), born in St Augustine, Florida (d. 1893)
- May 16 Levi Parsons Morton, (R) 22nd US VP (1889-93)
Ambrose Burnside (1824-1881)
May 23 American soldier, industrialist and politician (Governor of Rhode Island, 1866-69) who popularized sideburns, born in Liberty, Indiana
- May 29 Cadmus M. Wilcox, American Major General (Confederate Army - American Civil War), born in Wayne County, North Carolina (d. 1890)