Melvil Dewey, American librarian and educator, created the Dewey Decimal Classification (born 1851)

Melville Louis Kossuth "Melvil" Dewey was an American librarian and educator who invented the Dewey Decimal system of library classification. He was a founder of the Lake Placid Club, a chief librarian at Columbia College, founder of what would later become the Columbia University School of Library Service, and a founding member of the American Library Association. Although Dewey's contributions to the modern library are widely recognized, his legacy is marred by his sexual harassment of female colleagues, as well as his racism and antisemitism.

The Dewey Decimal Classification (DDC) colloquially known as the Dewey Decimal System, is a proprietary library classification system which allows new books to be added to a library in their appropriate location based on subject. It was first published in the United States by Melvil Dewey in 1876. Originally described in a 44-page pamphlet, it has been expanded to multiple volumes and revised through 23 major editions, the latest printed in 2011. It is also available in an abridged version suitable for smaller libraries. OCLC, a non-profit cooperative that serves libraries, currently maintains the system and licenses online access to WebDewey, a continuously updated version for catalogers.