The frontalis is the broad, flat muscle of your forehead, and its primary job is raising your eyebrows. Every time you look surprised, squint to read something far away, or widen your eyes during conversation, the frontalis is doing the work. It also creates the horizontal wrinkles that run across your forehead, which is why it plays such a central role in both facial expression and cosmetic treatments.
How the Frontalis Moves Your Forehead
The frontalis has one main action: it pulls the skin and soft tissue of the forehead upward, which elevates the eyebrows. This is the only muscle on the forehead capable of lifting the brows. When it contracts, the skin bunches into those characteristic horizontal creases.
This eyebrow-lifting action matters more than you might think. Raising the brows opens up the eye area, giving you a wider field of vision. People who lose frontalis function, whether from nerve damage or overtreatment with cosmetic injections, often notice their upper eyelids feel heavier and their forehead looks flat and expressionless. The muscle is constantly working in subtle ways throughout the day, adjusting brow position during conversation, reading, and emotional expression.
Where the Muscle Sits and How It’s Built
The frontalis covers most of the forehead. It doesn’t attach to bone the way many muscles do. Instead, its lower fibers blend into the skin and soft tissue near the eyebrows, interweaving with several smaller muscles around the eye. At the top, it connects to a tough, fibrous sheet called the galea aponeurotica, a tendon-like layer that stretches across the top of the skull like a cap.
The muscle actually has two separate bellies, one on each side of the forehead, with a gap between them near the midline. The size of that gap varies from person to person. Dissection studies have identified three main variations based on how much the two bellies overlap in the center. In some people, the muscle fibers only reach the inner two-thirds of the eyebrow rather than spanning the full width, which may contribute to a naturally downward-slanting brow shape. This kind of individual variation helps explain why the same cosmetic procedure can produce different results in different people.
The Frontalis and Its Opposing Muscles
The frontalis doesn’t work in isolation. It’s part of a tug-of-war system around the eyebrows. While the frontalis pulls the brows up, a group of smaller muscles pulls them down and inward. The corrugator supercilii draws the brows together and downward (creating the vertical “frown lines” between your eyes). The procerus pulls the skin between the brows downward. The upper fibers of the orbicularis oculi, the circular muscle that closes your eyelid, also pull the brow down.
Your resting brow position is the result of the balance between these forces. As the frontalis weakens with age or loses tone, the downward-pulling muscles gradually win, and the brows drop. This is one reason eyebrows tend to sit lower on the face as people get older. It’s also why cosmetic treatments targeting the frontalis need to be carefully balanced: weaken it too much, and the opposing muscles pull the brows down further than intended.
Part of a Larger Muscle System
The frontalis is technically the front portion of a larger muscle complex called the occipitofrontalis (sometimes called the epicranius). The back portion, the occipitalis, sits at the base of the skull near the back of the head. These two muscle bellies are connected by the galea aponeurotica, that fibrous sheet spanning the top of the skull. When the occipitalis contracts, it pulls the scalp backward. When the frontalis contracts, it pulls the scalp and forehead skin forward and upward. Together, they allow subtle movement of the entire scalp.
Nerve and Blood Supply
The frontalis is controlled by the temporal branch of the facial nerve, the same major nerve responsible for movement across most of the face. This branch runs along the side of the forehead, which makes it vulnerable during surgery in that area. Damage to this nerve branch can leave the frontalis partially or fully paralyzed on one side, causing a noticeably asymmetric brow.
The muscle has a rich blood supply fed by arteries coming from both the inner and outer branches of the major neck arteries. Two key vessels, the supratrochlear and supraorbital arteries, exit from the eye socket and travel upward along the forehead, splitting into shallow and deep branches. The shallow branches feed the muscle and skin, while the deeper ones supply the bone covering underneath. A third artery, the frontal branch of the superficial temporal artery, supplies the outer portion of the muscle. These vessels connect to each other in an extensive network, which is why forehead cuts tend to bleed heavily but also heal well.
Role in Cosmetic Treatments
The frontalis is one of the most commonly treated muscles in cosmetic medicine. Botulinum toxin injections (commonly known by brand names like Botox) temporarily weaken the muscle, reducing its ability to contract and smoothing out horizontal forehead lines. A typical treatment uses 10 to 20 units for women and 20 to 30 units for men, spread across 4 to 8 injection points on the forehead.
Placement matters. Injections need to stay at least 1.5 centimeters above the bony rim of the eye socket. Going too low risks weakening the muscle in the area closest to the brow, which can cause the eyebrow or even the upper eyelid to droop, a complication called ptosis. Targeting the mid and upper portions of the muscle is the safer approach. Because the frontalis is the only muscle that lifts the brow, overtreating it without also addressing the downward-pulling muscles can leave the forehead smooth but the brows heavy and low-set, creating a flat, unexpressive look that many people find unnatural.
One common strategy is to treat the frontalis with roughly half the dose used on the frown muscles between the brows. This keeps the system in balance: the frown muscles are weakened enough that the frontalis doesn’t have to work as hard to hold the brows up, and the frontalis itself is softened just enough to reduce lines without completely flattening the forehead.