An optical imaging system includes a first lens, a second lens, a third lens, a fourth lens, and a fifth lens sequentially disposed in ascending numerical order along an optical axis from an object-side surface of the first lens toward an imaging plane of the optical imaging system, wherein the conditional expression 11≤TTL/IMG_HT is satisfied, where TTL is a distance along the optical axis from the object-side surface of the first lens to the imaging plane, and IMG_HT is one-half of a diagonal length of the imaging plane.