Empetrum nigrum, the crowberry, black crowberry, mossberry, rockberry, or, in western Alaska, Labrador, etc., blackberry, is a flowering plant species in the heather family Ericaceae with a near circumboreal distribution in the Northern Hemisphere.

Empetrum nigrum is a low growing, evergreen shrub with a creeping habit. The leaves are 3–6 millimetres (1⁄8–1⁄4 inch) long, arranged alternately along the stem. The stems are red when young and then fade to brown. It blooms between May and June.

It is usually dioecious. The flowers are small and not very noticeable, with greenish-pink sepals that turn reddish purple. The round fruits are drupes, 4–6 mm (1⁄8–1⁄4 in) wide, usually black or purplish-black but occasionally red. Its fruit persists for an average of 92.7 days, and bears an average of 7.8 seeds per fruit. Fruits average 86.5% water, and their dry weight includes 14.4% carbohydrates and 12.2% lipids, which is possibly the highest lipid content of any fleshy fruit in Europe.

The species has a near circumboreal distribution in the Northern Hemisphere.

Empetrum nigrum grows in bogs and other acidic soils in shady, moist areas; it also grows in subalpine and alpine habitats in the Pacific Northwest.

The moth species Glacies coracina, Zygaena exulans, and Hadula melanopa feed on the plant.

The metabolism and photosynthetic parameters of Empetrum can be altered in winter-warming experiments.

Empetrum nigrum has allelopathic properties (e.g. hampering seed germination and root extension of other plants) but the strength of these are dependent on the soil type.