Radiation therapy (RT) is an integral part of treating all stages of lung cancer. Stereotactic ablative radiation therapy (SABR) has emerged as a standard treatment option for stage I-II patients with medically inoperable disease. Stage IIIA-IIIB disease is typically managed with definitive concurrent chemo-radiotherapy (CRT). Intensity modulated radiation therapy (IMRT) has enabled delivery of more potent RT dose while greatly limiting dose to surrounding normal organs, including lung, esophagus, and heart. SABR may have an expanding role in the treatment of stage IV patients, with new clinical trials exploring its combination with systemic immuotherapies.