The peroneus brevis is a muscle located in the lower leg, specifically on the lateral side of the fibula. It plays a crucial role in foot movement, particularly in eversion, which is the action of turning the sole of the foot outward. This muscle helps stabilize the ankle and supports activities such as walking and running. Originating from the lower two-thirds of the fibula, the peroneus brevis inserts into the base of the fifth metatarsal bone. It is innervated by the superficial peroneal nerve, which is responsible for its motor function. Injuries or strains to this muscle can lead to pain and instability in the ankle.