The pelvic venous system is complex, with the potential for numerous pathways of collateralization. Owing to stenosis or occlusion, both thrombotic and nonthrombotic entities in the pelvis may necessitate alternate routes of venous return. Although the pelvic venous anatomy and collateral pathways may demonstrate structural variability, a number of predictable paths often can be demonstrated on the basis of the given disease and the level of obstruction. Several general categories of collateral pathways have been described. These pathway categories include the deep pathway, which is composed of the lumbar and sacral veins and vertebral venous plexuses; the superficial pathway, which is composed of the circumflex and epigastric vessels; various iliofemoral collateral pathways; the intermediate pathway, which is composed of the gonadal veins and the ovarian and uterine plexuses; and portosystemic pathways. The pelvic venous anatomy has been described in detail in cadaveric and anatomic studies, with the aforementioned collateral pathways depicted on CT and MR images in several imaging studies. A comprehensive review of the native pelvic venous anatomy and collateralized pelvic venous anatomy based on angiographic features has yet to be provided. Knowledge of the diseases involving a number of specific pelvic veins is of clinical importance to interventional and diagnostic radiologists and surgeons. The ability to accurately identify common collateral patterns by using multiple imaging modalities, with accurate anatomic descriptions, may assist in delineating underlying obstructive hemodynamics and diagnosing specific occlusive disease entities. ©RSNA, 2022.