John William Weidemeyer (b. in Fredericksburg, Virginia, 26 April 1819; d. in Amityville, New York, 18 January 1896) was a writer and entomologist.
Among his first teachers was Alexander T. Stewart, and he completed his education at the Columbia College grammar school.
For several years he taught at various seminaries in Ohio, but subsequently settled in New York City, where he entered on a business career.
He made collections of lepidoptera, including a western North American species that was named in his honor, Limenitis weidemeyerii (Weidemeyer's Admiral).
Weidemeyer also published Real and Ideal: a Collection of Metrical Compositions by John W. Montclair (Philadelphia, 1865); Themes and Translations (New York, 1867); American Fish, and how to catch Them (1885); and From Alpha to Omega (1889).