Cortinarius ainsworthii is a species of webcap. It is known from central and Northern Europe, where it grows in a variety of habitats. The species was first described in 2020, and was named in honour of the mycologist A. Martyn Ainsworth. Along with five other British webcaps, C. ainsworthii was selected by Kew Gardens as a highlight of taxa described by the organisation's staff and affiliates in 2020.

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