Intraoperative radiotherapy (IORT) delivers high doses of radiation during surgery, first developed in the 1960s. It can be administered via brachytherapy or mobile linear accelerators, allowing immediate treatment of the tumour bed. IORT offers advantages over external beam radiation therapy, including reduced waiting times and improved precision. A target trial showed no significant survival differences compared to standard EBRT, but IORT may reduce non-breast cancer mortality.