This chapter offers a comprehensive anatomical and clinical guide to botulinum toxin type A (BoNT-A) injections for forehead rejuvenation. It explores the layered structure of the forehead, the functional dynamics of the frontalis muscle, and the mechanisms of wrinkle formation. Emphasis is placed on wrinkle pattern classification, injection depth, marking techniques, and individual variations based on race, sex, and anatomy. By integrating anatomical data, tailored dosing strategies, and safety considerations, this chapter provides clinicians with evidence-based insights for optimizing aesthetic outcomes while minimizing complications in the upper third of the face.