Cortinarius clandestinus is a species of fungus in the Cortinariaceae family.

[1] It was first described in 1932 by Calvin Henry Kauffman[1][2] from a specimen collected amongst moss under Douglas firs and hemlock at Lake Cushman, Washington.

The stem is equal or somewhat clavate, with yellowish veil fibrils and perhaps a ring demarcation.

[3] The European species Cortinarius melanotus is similar, with a brownish veil on the stem.

montanus is greenish, with a yellow veil when young and a tomentose cap.