Hyaluronic acid (HA)-based penile girth enhancement (PGE) represents a significant advancement in aesthetic urology, providing a minimally invasive, reversible, and biocompatible alternative to traditional surgical methods. This chapter traces the development of HA-based PGE and outlines the principles guiding its clinical application. Beginning with the initial clinical evaluation of HA fillers in PGE, it highlights key findings on efficacy and safety that established this technique as a viable option. Practical considerations including patient selection, injection techniques, postoperative care, and complication management are discussed in detail. Emerging evidence supporting secondary benefits, such as improved ejaculatory control, and future innovations in filler technology are also explored. Together, these insights offer a comprehensive framework for clinicians seeking to integrate HA-based PGE into their practice safely and effectively.