Phlegmacium boreicyanites is a species of mushroom-forming fungus in the family Cortinariaceae. Originally described in 2014 as a member of the genus Cortinarius, it was reclassified in 2022 based on genetic data. The specific epithet boreicyanites reflects both its relationship to C. cyanites and its northern distribution. The species is characterised by its bluish grey cap that fades to pale greyish brown, gills that change from greyish blue to brownish violet with age, and a greyish blue club-shaped stipe with distinctive girdles. The fungus grows primarily in boreal mixed forests of northern Europe, forming mycorrhizal associations with spruce, birch, and poplar trees, and produces fruiting bodies during autumn months.

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