A gas sensor includes a sensor element, an inner protective cover having inside a sensor element chamber and having an element chamber inlet and an element chamber outlet, and an outer protective cover having an outer inlet and an outer outlet. On a side in a downward direction with respect to the element chamber inlet, a minimum distance between the inner protective cover and the sensor element is 2.64 mm or greater. When imaginary light parallel to an axial direction of the outer outlet is irradiated from an outside of the outer protective cover to the outer outlet, the imaginary light does not reach the sensor element chamber. A minimum flow channel width of an outlet-side gas flow channel that is formed as a space between the outer protective cover and the inner protective cover is 0.67 mm or greater and 2.60 mm or less.