A varifocal lens that corrects aberrations in the visible and near-infrared regions includes, in order from the object side, a first lens group of positive refractive power, a second lens group of negative refractive power, and third and fourth lens groups, each of positive refractive power. The second lens group moves along the optical axis to vary the focal length, and the fourth lens group is independently movable to compensate for movement of the image plane due to movement of the second lens group during varifocal adjustment. Aspheric lens surfaces are disclosed. Certain conditions are satisfied that relate to Abbe number and index of refraction of different lens elements, the distance between the first and third lens groups, the chromatic aberration and focal length of the first lens group, and the movement of the second lens group and the focal length change associated with this movement.