Depressor septii is a small muscle in the upper lip originating in the upper jaw bone and inserting into the septum and ala of the nose, and is located between the lower part of the nose and the orbicularis oris. It acts to lower the septum and nostril wings and change the shape of the nostril, narrowing and lengthing it. It is considered by some to be a part of nasalis.

Depressor septii is innervated by the lower zygomatic and buccal branches of the facial nerve (VII) and is supplied with blood by the facial artery.