Scirpus is a genus of aquatic, grass-like species in the family Cyperaceae (the sedges), many with the common names club-rush or bulrush (see also bulrush for other plant genera so-named). Other common names are deergrass or grassweed. They have grass-like leaves, and clusters of small spikelets, often brown. Some species (e.g. S. lacustris) can reach a height of 3 m, while others (e.g. S. supinus) are much smaller, only reaching 20–30 cm tall.
The genus has a nearly cosmopolitan distribution, found on every continent except Africa and Antarctica. Many species are common in wetlands and can produce dense stands of vegetation, along rivers, in coastal deltas and in ponds and potholes. Although flooding is the most important factor affecting its distribution, drought, ice scour, grazing, fire and salinity also affect its abundance. It can survive unfavourable conditions like prolonged flooding, or drought, as buried seeds
Scirpus species are often planted to inhibit soil erosion and provide habitat for other wildlife. They are also used in some herbal remedies; the plant's rhizomes are collected in the autumn and winter and dried in the sun before use.