The Peroneus Tertius is a muscle located in the lower leg, specifically in the lateral compartment. It originates from the lower part of the fibula and inserts into the fifth metatarsal bone of the foot. This muscle plays a role in dorsiflexion and eversion of the foot, helping to lift the foot and turn it outward. Not everyone has a Peroneus Tertius, as it is considered an anatomical variant. Its presence can vary among individuals, and it is more commonly found in certain populations. Understanding this muscle is important for studying lower limb function and potential injuries related to the ankle and foot.