Boletus fibrillosus, commonly known as the fib king,[2] is a basidiomycete fungus of the genus Boletus found in western North America.

The fruiting bodies are found in mixed coastal forests in the fall, usually singly or in small groups.

The tubes are yellow, while the flesh is white to buff and does not stain when cut.

The stem is yellowish at the top, brown otherwise, with a reticulate texture,[1][4] and mycelium enshrouding the bottom.

[5] Phylogenetic analysis has shown B. fibrillosus as a member of a clade, or closely related group, with B. pinophilus, B. regineus, B. rex-veris, B. subcaerulescens, and Gastroboletus subalpinus.