The mentalis muscle is a paired muscle located at the lower end of the chin, which acts as the primary muscle of the lower lip.

This muscle originates from the mandible (lower jaw), and provides stability to the lower lip to allow it to pout. It causes protrusion of the lower lip and elevates the skin of the chin. As the lower lip is raised, it results in elevation and wrinkling of the chin's skin. The mentalis is so named because of its association with emotional and thoughtful facial expressions.

The zygomatic facial nerve supplies this muscle, and the facial artery is its source of blood supply.

The mentalis is generally not associated with any facial problems, but in rare cases it may result in medical disorders. One of the movement disorders caused by the mentalis muscle is referred to as geniospasm, which causes uncontrollable tremors of the chin and lower lip. This is a harmless condition that usually begins in childhood and may occur due to genetic factors. This can be a socially problematic condition for the patient and may require medical care.