Locally advanced human papillomavirus (HPV)-associated gynecologic cancers, including cervical, vaginal, and vulvar cancers, are treated primarily with radiation therapy (RT). Cervical cancer remains a leading cause of cancer death among women worldwide. The superior soft-tissue resolution of MRI compared with other imaging modalities makes it an ideal modality for RT planning, execution, and follow-up of these malignancies. This superiority has been corroborated in the literature when comparing MRI-based RT planning to radiography-based conventional treatment planning approaches. In 2005, the Groupe Européen de Curiethérapie and the European Society for Radiation Therapy and Oncology guidelines underscored the central role of MRI for successful implementation of three-dimensional image-based cervical cancer brachytherapy. The delineation of both gross tumor volume and clinical tumor volume for brachytherapy is performed at the time of each brachytherapy application, on the basis of the findings depicted on anatomic MR images. Contemporary knowledge concerning the role of MRI for RT planning in HPV-associated gynecologic cancers warrants an understanding of the epidemiology and clinical manifestations of these cancers, as well as knowledge of MRI protocol for cancer staging, selection of RT candidates, brachytherapy implant assessment, posttreatment surveillance, and delineation of treatment-related complications. Technical requirements, patient preparation, and image acquisition protocols are detailed in this review, and imaging-based treatment protocols are summarized. Knowledge of these fundamental concepts enables the radiologist to play an important role in diagnosis, staging, and posttreatment follow-up, helping to guide radiation oncologists and other clinicians in the management of these malignancies.©RSNA, 2019.