Populus nigra, the black poplar, is a species of cottonwood poplar, the type species of section Aigeiros of the genus Populus, native to Europe, southwest and central Asia, and northwest Africa.

It is a medium-sized to large deciduous tree, reaching 20–30 m (rarely 40 m) tall, with a trunk up to 1.5 m diameter, though some old individuals have grown much bigger (more than 3 meters DBH for several trees in France). The leaves are diamond-shaped to triangular, 5–8 cm long and 6–8 cm broad, green on both surfaces. The species is dioecious (male and female flowers on different plants), with flowers in catkins and pollination by wind. The black poplar grows in low-lying areas of moist ground.