Understanding the anatomy of the penis is crucial for safe and effective penile augmentation using injectable hyaluronic acid gel. This chapter aims to detail the macro- and microanatomical structures of the penis, emphasizing their relevance to augmentation techniques. Particular focus is placed on the vasculature, innervation, and fascias, such as Buck’s and Dartos fascia, which play significant roles in procedural success. Unlike conventional penile anatomy, the anatomy of the glans penis and the penile skin were added for better understanding of the techniques of glans penis augmentation and penile girth enhancement using fillers.