Garnier is a surname commonly found in France and Québec. Derivations from the original include Gagné, Grenier, and Gasnier. Garnier is a very common name in France, although not as much in Québec due to the various spelling changes since the 17th century when it was first introduced there. Notable people with the surname Garnier include:
- Saint Charles Garnier, Jesuit missionary martyred in Canada in 1649
- Charles Garnier (architect), 19th-century French architect
- Tony Garnier (architect), French architect
- Tony Garnier (musician), American bassist
- Edward Garnier, British politician
- Octave Garnier, French anarchist
- Laurent Garnier, French musician and DJ
- Robert Garnier, French poet
- Francis Garnier, French explorer
- G. Garnier, French economist and translator of Adam Smith
