FLASH radiotherapy (FLASH-RT) is an emerging technique that delivers radiation at ultra-high dose rates, offering the potential to achieve equal or superior tumour control compared to conventional radiotherapy, while significantly reducing toxicity to surrounding healthy tissues. Experimental studies have consistently demonstrated tissue-sparing effects, and early clinical experiences suggest potential benefits in sensitive patient groups, such as children or those requiring re-irradiation. Although the precise biological mechanisms are not yet fully understood, the observed protective effects suggest a complex interplay of physicochemical and cellular processes. The translation of FLASH-RT into clinical practice was still limited by significant technological challenges, particularly in dosimetry, beam generation, and treatment delivery. Nevertheless, the rapid pace of research and the promising balance between safety and efficacy highlight FLASH-RT as a potential breakthrough in the future of cancer therapy.