The Coppermine River in western Nunavut is one of Canada's great Arctic rivers, yet its vascular plant flora is poorly known. Here, we report the results of a floristic inventory of the lower Coppermine River valley and vicinity, including Kugluk (Bloody Falls) Territorial Park and the hamlet of Kugluktuk. The study area is approximately 1200 km 2 , extending from the forest-tundra south of the treeline to the Arctic coast. Vascular plant floristic data are based on a review of all previous collections from the area and more than 1200 new collections made in 2014. Results are presented in an annotated checklist, including citation of all specimens examined, comments on taxonomy and distribution, and photographs for a subset of taxa. The vascular plant flora comprises 300 species (311 taxa), a 36.6% increase from the 190 species documented by previous collections made in the area over the last century, and is considerably more diverse than other local floras on mainland Nunavut. We document 207 taxa for Kugluk (Bloody Falls) Territorial Park, an important protected area for plants on mainland Nunavut. A total of 190 taxa are newly recorded for the study area. Of these, 14 taxa (13 species and one additional variety) are newly recorded for Nunavut (Allium schoenoprasum, Carex capitata, Draba lonchocarpa, Eremogonecapillaris subsp. capillaris, Sabulina elegans, Eleocharis quinqueflora, Epilobium cf. anagallidifolium, Botrychium "neolunaria", B. tunux, Festuca altaica, Polygonum aviculare, Salix ovalifolia var. arctolitoralis, S. ovalifolia var. ovalifolia and Stuckenia pectinata), seven species are newly recorded for mainland Nunavut (Carex gynocrates, C. livida, Cryptogramma stelleri, Draba simmonsii, Festuca viviparoidea subsp. viviparoidea, Juncus alpinoarticulatus subsp. americanus and Salix pseudomyrsinites) and 56 range extensions are reported. PsbA-trnH and rbcL DNA sequence data were used to help identify the three Botrychium taxa recorded in the study area. Three new combinations are proposed: Petasites frigidus subsp. sagittatus (Banks ex Pursh) Saarela, Carex petricosa subsp. misandroides (Fernald) Saarela and Carex simpliciuscula subsp. subholarctica (T.V. Egorova) Saarela.