紫竹（学名：Phyllostachys nigra），又称黑竹，为刚竹属植物。

圆筒形的秆高3－5米、直径2－4厘米，成长后渐变为紫黑色；箨鞘新鲜时为淡红色或带黄绿色，没有斑点，有细毛，干后变枯草色，具紫色或灰褐色的斑点或条纹，容易脱落，绿色短小的箨叶，有皱折；2－3片叶子生于小枝顶端，细长披针形叶片极薄；扇形小穗丛，常2－4枚集生于最后小枝的顶端，小穗含有3或4朵小花，七月开花。

Phyllostachys nigra, common name black bamboo, is a species of flowering plant in the bamboo subfamily of the grass family Poaceae, native to Hunan Province of China, and widely cultivated elsewhere.

Growing up to 5 m (16 ft) tall by 3 m (10 ft) broad, it forms clumps of slender arching canes which turn black after two or three seasons. The abundant lance-shaped leaves are 4–13 cm (2–5 in) long.