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