An optical system includes an optical element made of resin and a reflection portion configured to reflect ultraviolet radiation. The reflection portion is provided on an optical surface located closer to an object side than the optical element, and conditional expressions 0.10≤Lu/L≤0.90 and |tan−1(H0/Lr)−tan−1{H0(Lr−Lu)/(Ru×Lr)}|≤25° are satisfied, in which H0 represents a maximum height, from an optical axis, of an optical surface closest to the object side, Lu represents a distance from the optical surface closest to the object side to the reflection portion, Lr represents a distance from the optical surface closest to the object side to the optical element, L represents a total length of the optical system, and Ru represents a radius of curvature of the optical surface on which the reflection portion is provided.