Hydnellum underwoodii is an inedible species of tooth fungus in the family Bankeraceae.

[3] Found in North America, it was described as new to science in 1906 by American mycologist Howard James Banker.

[4] Its reddish-brown, convex to flattened cap measures 5–14 cm (2.0–5.5 in) in diameter.

Spines on the cap underside are 1–3 mm long; they are initially white, becoming brown with grayish tips in age.

The fungus fruits singly or scattered, on the ground in coniferous forests.