A zoom lens includes, in order from an object side to an image side, a positive first lens unit, a negative second lens unit, a positive third lens unit, and a positive fourth lens unit. During zooming from a wide-angle end to a telephoto end, the first lens unit moves with a locus convex toward the image side, and the third lens unit moves toward the object side. The first lens unit includes, in order from the object side to the image side, a negative first lens, a positive second lens, and a positive third lens. A distance (d12) between the first lens and the second lens, a focal length (fw) of the entire zoom lens at the wide-angle end, and a refractive index (Np) of a positive lens having the lowest refractive index among the refractive indices of materials of all positive lenses included in the first lens unit are appropriately set based on predetermined mathematical conditions.