Zagayowar Carnot wani tsarin zagayowar thermodynamic ne na ka'idar da ke bayyana hanya mafi inganci ta canza zafi zuwa aiki. Ya ƙunshi matakai guda huɗu masu juyawa: haɓaka isothermal, fadada adiabatic, matsawar isothermal, da matsawar adiabatic. Ana kiran wannan zagayowar ne bayan masanin kimiyyar lissafi na Faransa Nicolas Léonard Sadi Carnot, wanda ya gabatar da manufar a cikin littafinsa na 1824 mai suna "Reflections on the Motive Power of Fire."