An applicator for intraoperative radiotherapy with low-energy X-ray radiation includes an applicator body, an air-permeable outer surface with a circumferential outer face and with a distal end, a receiving device which is arranged at a proximal end and with which the applicator can be secured to an X-ray irradiation device, and an inner recess which has an opening at the proximal end and into which an X-ray radiation source is insertable. The applicator has a solid porous structure on its outer surface which provides the air-permeable outer surface with a rigid shape. The solid porous structure forms a continuous air-permeable channel structure which is connected in an air-conducting manner to the proximal end of the applicator.