Russula vinosa, commonly known as the darkening brittlegill, is a species of basidiomycete mushroom found in coniferous woodlands in Europe and North America in summer and early autumn.

It is usually understood to have a symbiotic relationship with evergreen tree roots, except for in mountainous areas where it has occasionally associated with birches.

The specific epithet "vinosa" is derived from the Latin vinum "wine", likely alluding to the wine-colored cap of this species that is capable of acting as a dye.

The cap is concave and wine to red-brown in colour, often fading to a pale white or tan in the center with age.

The red-capped color of Russula vinosa is almost impossible to visually separate from other toxic and inedible red-capped Russulas, such as the bloody brittlegill (R. sanguinaria), the sickener (R. emetica), and the beechwood sickener (R. nobilis).