Dethier is a surname. Notable people with this surname includes:
Édouard Dethier (1885-1962), Belgian classical violinist Gaston Dethier (1849-1933), American classic composer Nicolas Dethier (1888–1976), Belgian trade unionist and politician Sylvia Dethier (born 1965), retired Belgian athlete Victor Dethier (1892–1963), Belgian racing cyclist Vincent Dethier (1915–1993), American physiologist and entomologist