Herein,　a　novel　cyclometalated　iridium　(III)　complex　(Ir-1)　with　good　water-solubility　was　designed　and　synthesized　to　sensitively　detect　hypochlorite　(ClO−)　in　aqueous　buffer　solution.　The　sensor　Ir-1　was　prepared　by　incorporating　a　methacrylate　group　into　cyclometalated　ligands,　which　was　a　specific　response　site　toward　ClO−　through　an　oxidation　process.　Ir-1　displayed　strong　emission　at　615　nm,　while　significant　fluorescence　quenching　was　observed　upon　addition　of　ClO−　with　a　low　detection　limit　of　0.41　μM.　Moreover,　probe　Ir-1　exhibited　a　rapid　response　(<30　s)　for　ClO−　with　high　selectivity　over　potentially　competing　species.　The　sensing　process　was　evidenced　by　NMR　and　MS　characterization.　Further　application　in　bioimaging　of　ClO−　was　successfully　performed　in　living　HepG2　cells.　©　2019