Extrachromosomal　circular　DNA　(eccDNA)　has　emerged　as　a　critical　area　of　cancer　research　due　to　its　ubiquitous　presence　in　tumour　cells　and　significant　role　in　tumorigenesis,　progression　and　drug　resistance.　Recent　studies　demonstrate　that　eccDNA　promotes　cancer　progression　by　influencing　genomic　instability,　amplifying　oncogenes,　regulating　gene　expression　and　enhancing　tumour　cell　adaptability　to　adverse　conditions.　While　the　precise　mechanisms　underlying　eccDNA　formation　and　its　biological　functions　remain　unclear,　its　potential　applications　in　cancer　diagnosis,　prognosis　and　targeted　therapy　are　gaining　increasing　recognition.　This　review　summarises　the　latest　advancements　in　eccDNA　research,　highlighting　its　potential　as　both　a　biomarker　and　a　therapeutic　target.　Additionally,　it　emphasises　the　translational　potential　of　eccDNA　in　clinical　diagnostics　and　personalised　treatment　strategies,　offering　new　perspectives　for　future　cancer　research　and　innovative　therapies.