Radiation treatment, also known as radiotherapy, is one of the key treatment modalities for prostate cancer. In this chapter, a comprehensive examination of the mechanisms, modalities, and applications of radiation treatment within a multidisciplinary framework is provided. First, the fundamental mechanisms through which ionizing radiation mediates cancer cell death before exploring various treatment modalities, such as external beam radiation therapy (EBRT) and brachytherapy, with a focus on the technical aspects of these techniques are discussed. Over the past few decades, these techniques have rapidly advanced, leading to development of more sophisticated treatment modalities, such as intensity-modulated radiation therapy (IMRT), which have further improved precision and efficacy of treatment delivery. The application of radiation treatment in different stages of prostate cancer, from newly diagnosed with no prior treatments, recurrent disease following prostatectomy in the salvage setting, emphasizing the importance of tailoring treatment to each individual patient, is examined. Additionally, the growing role of metastasis-directed radiation therapy in advanced prostate cancer, showcasing its potential to enhance both local tumor control and systemic outcomes, is reviewed. Recent advances in theranostics, including radium-223 and lutetium-177–labeled prostate-specific membrane antigen (Lu-PSMA-177), have further expanded the therapeutic landscape by enabling targeted radiopharmaceutical approaches that deliver localized radiation while simultaneously providing diagnostic imaging capabilities. Finally, this chapter addresses the common radiation-induced toxicities with radiation of prostate cancer, encompassing both acute and late complications. By integrating evidence-based practices with emerging technological advancements, this chapter will equip clinicians and surgeons with an introductory understanding of the role of radiation treatment in the management of prostate cancer across the disease spectrum.