mesquite, (genus Prosopis), genus of spiny deep-rooted shrubs or small trees in the pea family (Fabaceae). They form extensive thickets in areas from South America into the southwestern United States. They are considered pests and have been eradicated in some places. The wood of the mesquite, formerly used in railroad ties, is of limited economic value, though it is useful for unusual furniture and for aromatic firewood.

Mesquite roots penetrate depths of as much as 20 metres (70 feet) in search of water. Their trunks may be 45 cm (18 inches) in diameter but more commonly are smaller or shrublike. The plants bear compound leaves with numerous narrow olive-green to white hairy leaflets. The flowers occur in dense cream-coloured or yellow catkins about 8 cm (3 inches) long and are followed by clusters of long, narrow, pale yellow beans 15–20 cm (6–8 inches) long. The beans, which contain a sweet pulp, are often eaten by cattle.