Arachnomyces is a genus of cleistothecial ascomycete fungi described in 1902, of which the anamorph (asexual) stage is the genus Onychocola. Although morphologically similar to members of other families, the fungus now belongs to its own monotypic family Arachnomycetaceae, which is the only family in the monotypic order Arachnomycetales.