Penile girth enhancement (PGE) has undergone remarkable evolution, transitioning from invasive and high-risk procedures to safe, minimally invasive techniques utilizing hyaluronic acid (HA) gel. Since the publication of the first prospective clinical study on PGE with HA gel by Kwak et al. in 2011, an expanding body of evidence—including randomized controlled trials, meta-analyses, and systematic reviews—has validated the efficacy and safety of this approach. This chapter provides a comprehensive synthesis of current literature, offering critical insights into clinical outcomes, complications, injection techniques, and the role of HA fillers as a preferred alternative to traditional augmentation methods.