- Dewey, George 1837-1917; U.S. admiral in the Spanish-American War
- Dewey, John 1859-1952; U.S. philosopher & educator: exponent of pragmatism
- Dewey, Melvil (born Melville Louis Kossuth Dewey) 1851-1931; U.S. librarian & educator: originator of a system () for book classification in libraries, using three-digit numbers, further extended beyond a decimal point for subclasses
- An American surname.
- A male given name derived from the surname, popular in the U.S. in the 1890s.
Possibly from a place name in Northern France, Douai. Welsh origin from Dewi (David) has also been suggested.