The lateral compartment of endometriosis is estimated to be lower than 15% but considered as a critical location of endometriosis for symptoms and complications. The anatomy of this compartment is complex and includes the anterolateral parametrium, mediolateral parametrium, and posterolateral parametrium (i.e., the sacrorectal septum, also known as the visceral pelvic fascia). It may involve multiple structures, such as the ureter, uterine artery, hypogastric artery and nerves, and inferior hypogastric plexus (or pelvic plexus). Therefore, the description of this location is crucial to inform patients undergoing surgery of the necessity of a resection such as parametrectomy, which is associated with a high risk of postoperative complications: ureteral injury causing the possibility of ureteral fistula and/or urinary or anorectal dysfunction due to nerve injury. In this chapter, we will describe the classical anatomy but also the surgical anatomy, explaining potential discrepancies caused by surgical dissection. We will then present radiological definitions and imaging aspects. Finally, radiosurgical correlations will allow us to better understand the surgical impacts of radiological descriptions and the need for a reproductive classification for lateral endometriosis. These radiological descriptions are critical to give patients adequate information on their disease and, if needed, preoperative risks and personalized treatment counseling.