Demby is a surname. Notable people with the surname include:
Albert Joe Demby (born 1934), Sierra Leonean politician and Vice President
Constance Demby (born 1939), US musician, composer, artist
Edward Thomas Demby (1869-1957), US author and religious figure
Jack Demby, one of the names used by Austrian football athlete (1888-1963)
William Demby (1922–2013), American writer