Barbed wire, also known as barb wire, is a type of steel fencing wire constructed with sharp edges or points arranged at intervals along the strands. Its primary use is the construction of inexpensive fences, and it is also used as a security measure atop walls surrounding property. As a wire obstacle, it is a major feature of the fortifications in trench warfare.

A person or animal trying to pass through or over barbed wire will suffer discomfort and possibly injury. Barbed wire fencing requires only fence posts, wire, and fixing devices such as staples. It is simple to construct and quick to erect, even by an unskilled person

Wire fences are cheaper and easier to erect than their alternatives (one such alternative is Osage orange, a thorny bush that is time-consuming to transplant and grow).[5] When wire fences became widely available in the United States in the late 19th century, it became more affordable to fence much larger areas than before, and intensive animal husbandry was made practical on a much larger scale.