Despite numerous efforts over the past several decades, few therapeutic breakthroughs in the treatment of GBM have been realized, and even these have yielded only incrementally modest gains. Radiotherapy remains a crucial component in the management of this disease. In this review, the historical basis for inclusion of radiotherapy as part of the therapeutic regimen for GBM is examined. Additionally, an overview of the evidence supporting the modern role of radiotherapy is provided along with a discussion of standard and emerging combined modality therapies. Finally, GBM management guidelines from three professional societies are reviewed.