Barbed wire, also known as barb wire (and frequently in dialect form spelled bob or bobbed), is a type of fencing wire constructed with sharp edges or points arranged at intervals along the strand. It is used to construct inexpensive fences and is used atop walls surrounding secured property. It is also a major feature of the fortifications in trench warfare (as a wire obstacle).

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.