[9] The fruit bodies of Butyriboletus regius have caps that are initially convex before flattening out in maturity, reaching a diameter of 7–20 cm (2.8–7.9 in) wide.

Initially velvety to slightly tomentose (hairy) when young, these minute hairs tend to slough off with age, and the cap develops wrinkles and pits.

Its smooth, hyaline (translucent) spores are roughly elliptical to somewhat fusoid (wider in the middle and tapering toward the ends) to more or less cylindrical, and have dimensions of 12–17 by 4–5 μm.

[4] Butyriboletus regius is an ectomycorrhizal species with a broad host range,[10] and associates with oak and conifers, particularly fir.

The North American distribution includes the Pacific Northwest states of California, Oregon, and Washington, where its frequency of occurrence ranges from "rare to locally abundant".

[4] It is rare in Europe, appearing on the Regional Red List of several countries,[11] and is considered endangered in the Czech Republic.