This　paper　reports　novel　imidazole　fluorescent　poly(ionic　liquid)　nanoparticles　(FPILNs)　of　poly(1-[(4-methyphenyl)methyl]-3-vinyl-imidazolium　bromide　(poly([MVI]Br)　for　selective　and　sensitive　determination　of　pyrogallol.　An　imidazole　ionic　liquid　of　1-[(4-methyphenyl)methyl]-3-vinyl-imidazolium　bromide　([MVI]Br)　was　synthesized　and　used　as　the　only　monomer　to　obtain　poly([MVI]Br)　possessing　phenyl　fluorophores　using　a　radical　polymerization　technique.　The　obtained　poly([MVI]Br)　can　form　nanoparticles　in　water.　Scanning　electron　microscopy　and　dynamic　light　scattering　results　revealed　majority　of　poly([MVI]Br)　FPILNs　with　diameters　ranging　from　40　to　400 nm.　Although　[MVI]Br　showed　weak　fluorescence　intensity,　poly([MVI]Br)　FPILNs　exhibited　strong　fluorescence　intensity　with　a　quantum　yield　of　0.192,　which　is　attributed　to　the　presence　of　significant　number　of　phenyl　fluorophores　and　rigid　construction.　The　selective　and　sensitive　determination　of　pyrogallol　was　achieved　through　fluorescence　quenching　of　poly([MVI]Br)　FPILNs,　and　the　quenching　was　attributed　to　the　oxidation　of　poly([MVI]Br)　FPILNs　by　O2˙¯　produced　by　pyrogallol　autoxidation.　The　poly([MVI]Br)　FPILNs-based　sensor　demonstrated　a　good　linear　relationship　between　the　extent　of　fluorescence　quenching　and　the　concentration　of　pyrogallol　in　a　range　of　0.05　–　10.0 μM,　achieving　a　detection　limit　of　0.01 μM.　Furthermore,　the　poly([MVI]Br)　FPILNs-based　assay　detected　pyrogallol　in　environmental　water　samples,　suggesting　its　potential　to　be　applied　for　practical　purposes.　©　2017　Elsevier　B.V.