An optical system includes a plurality of lens units. The lens units consisting of, in order from an object side to an image side, a first lens unit, a second lens unit having positive refractive power, a third lens unit, a fourth lens unit having positive refractive power, and a fifth lens unit. During focusing, the first lens unit, the third lens unit, and the fifth lens unit are fixed, and the second lens unit and the fourth lens unit move. The second lens unit consists of one lens component. The third lens unit includes at least one positive lens and one negative lens. The fourth lens unit includes at least two positive lenses and one negative lens.