The jawline is a defining feature of facial structure, contributing significantly to the perception of youth, attractiveness, and gender characteristics. A two-layer technique using hyaluronic acid filler is described to enhance mandibular definition, including the angle, body, and pre-jowl area. Structural support is achieved with deep supraperiosteal injections, while superficial filler placement improves contour transitions and refines lower face aesthetics. Key anatomical landmarks, aesthetic ideals, and vascular considerations are reviewed to guide safe and effective treatment. A clinical case, injection technique, post-treatment care, complications, limitations, and pearls are provided to support consistent, natural-looking results.