Nanomaterials　with　enzyme-mimicking　properties,　coined　as　nanozymes,　are　a　promising　alternative　to　natural　enzymes　owing　to　their　remarkable　advantages,　such　as　high　stability,　easy　preparation,　and　favorable　catalytic　performance.　Recently,　with　the　rapid　development　of　nanotechnology　and　characterization　techniques,　single　atom　nanozymes　(SAzymes)　with　atomically　dispersed　active　sites,　well-defined　electronic　and　geometric　structures,　tunable　coordination　environment,　and　maximum　metal　atom　utilization　are　developed　and　exploited.　With　superior　catalytic　performance　and　selectivity,　SAzymes　have　made　impressive　progress　in　biomedical　applications　and　are　expected　to　bridge　the　gap　between　artificial　nanozymes　and　natural　enzymes.　Herein,　the　recent　advances　in　SAzyme　preparation　methods,　catalytic　mechanisms,　and　biomedical　applications　are　systematically　summarized.　Their　biomedical　applications　in　cancer　therapy,　oxidative　stress　cytoprotection,　antibacterial　therapy,　and　biosensing　are　discussed　in　depth.　Furthermore,　to　appreciate　these　advances,　the　main　challenges,　and　prospects　for　the　future　development　of　SAzymes　are　also　outlined　and　highlighted　in　this　review.　©　2023　Wiley-VCH　GmbH.