This chapter extensively covers the definition, pathophysiology, diagnosis, and management of erectile dysfunction (ED). It includes neurovascular, hormonal, and psychological causes. Pharmacologic and non-pharmacologic treatments are reviewed, including PDE5 inhibitors, vacuum devices, intracavernosal injections, and penile prostheses. According to the most recent guidelines endorsed by the Italian Society of Andrology and Sexual Medicine (SIAMS) and aligned with the European Academy of Andrology, erectile dysfunction should be considered a multidimensional disorder with vascular, endocrine, neurological, and psychological components, requiring a structured diagnostic and therapeutic approach based on cardiovascular risk stratification and patient-centered management.