In the military science of fortification, wire obstacles are defensive obstacles made from barbed wire, barbed tape or concertina wire. They are designed to disrupt, delay and generally slow down an attacking enemy. During the time that the attackers are slowed down by the wire obstacle (or possibly deliberately channelled into killing zones) they are easy to target with machinegun and artillery fire. Depending on the requirements and available resources, wire obstacles may range from a simple barbed wire fence in front of a defensive position, to elaborate patterns of fences, concertinas, "dragon's teeth" and minefields hundreds of metres thick.

One example is "low wire entanglement", which consists of irregularly placed stakes that have been driven into the ground with only some 15 cm (six inches) showing. The barbed wire is then wrapped and tightened on to these. An enemy combatant running through the barrier, which is difficult to see, is apt to trip and get caught.

Wire obstacles may have originated with Union General Ambrose Burnside during the American Civil War Battle of Fort Sanders in the Knoxville Campaign, when telegraph wire was strung between tree stumps 30 to 80 yards in front of one part of the Union line. They first saw significant military use during the Second Boer War, and reached their pinnacle during World War I where, together with machine guns, they were responsible for many casualties in the trench warfare that dominated that conflict and gave the defending side substantial advantage.