Black locust (Robinia pseudoacacia) is a tall hardwood common in North America. 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, its pods are quite toxic. In fact, every part of the tree is considered toxic; there have even been rare cases of illness even from consuming the honey made from the flowers of the tree.

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.

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 big size and rapid growth, but there exists 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 extremly hard wooded and long lasting, making it prized for fence posts. As a young man, Abraham Lincoln spent a lot of time splitting rails and fence posts from black locust logs.