Radiation therapy (RT) is an indispensable component in the multidisciplinary management of breast cancer. In the past few years, hypofractionated whole breast irradiation has gained significance and it is replacing standard five-week whole breast adjuvant radiation. Further, with a better understanding of the radiation biology of the tumour and normal breast tissue/s, various ultra-hypofractionated regimens are under evaluation. In a select group of patients, five-fraction WBI regimens have been accepted already. Also, in selected patients with a low risk of recurrence, partial breast irradiation (PBI) has been used with or without acceleration, which has resulted in a reduction of treatment duration as well as the volume of the irradiated breast tissue. After a follow-up of 10 years or more, several randomised trials have demonstrated adequate and acceptable safety and efficacy of PBI. The hypo-fractionated approach has demonstrated comparable outcomes in patients requiring regional nodal irradiation after undergoing BCS or mastectomy without oncoplastic reconstruction. The role of radiation is well known in the management of oligometastatic disease, where high-dose radiation can be delivered to metastatic sites by the SABR (stereotactic ablative body radiation) technique. Radiation has been used in palliative care, which comprises pain management due to skeletal metastasis; whole brain irradiation and SRS (stereotactic radiosurgery) for brain metastasis; haemostatic radiation to control tumour-related bleeding and palliative radiation for extensive fungating lesion not responding to other treatment modality. Apart from the malignant condition of the breast, RT has also been used for benign breast conditions like Phyllodes tumour and refractory gynecomastia. This chapter is an attempt to introduce various techniques and their utility in different scenarios to the readers.