Black locust (Robinia pseudoacacia) is a tree in the subfamily Faboideae of the pea family Fabaceae. It is native to eastern North America from northeast Texas to New York, and widely planted and naturalised elsewhere in the rest of temperate North America, Europe and Asia. Similar in appearance to honey locust, it lacks that tree's characteristic spines.

As with honey locust, black locust reproduces through distinct hanging pods. However, unlike honey locust, but like the related European Laburnum, its pods are toxic. In fact, every part of the tree is considered toxic.

Black locust is a major honey plant in eastern USA, and, having been taken and planted in France, is the source of the renowned acacia monofloral honey from France. Flowering starts after 140 growing degree days.

In Europe it is often planted alongside streets and in parks, especially in large cities, because it tolerates pollution well. The species is unsuitable for small gardens due to its large size and rapid growth, but there are cultivars that make good garden plants.

Black locust is a legume in the family Fabaceae, which makes it capable of hosting nitrogen-fixing bacteria on its root system. It is extremely hard wooded, resistant to rot and long lasting, making it prized for fence posts and small watercraft. As a young man, Abraham Lincoln spent a lot of time splitting rails and fence posts from black locust logs.

Some other species of Robinia are:
Robinia hispida - Rose locust
Robinia neomexicana - New Mexican locust