A land mine, or landmine, is an explosive weapon often concealed under or camouflaged on the ground, and designed to destroy or disable enemy targets as they pass over or near it. Land mines are divided into two types: anti-tank mines, which are designed to disable tanks or other vehicles; and anti-personnel mines, designed to injure or kill people.

Land mines are typically pressure activated, exploding automatically when stepped on by a person or driven over by a vehicle, though alternative detonation mechanisms are sometimes used. A land mine may cause damage by direct blast effect, by fragments that are thrown by the blast, or by both. Land mines are typically laid throughout an area, creating a minefield which is dangerous to cross.

The use of land mines is controversial because of their indiscriminate nature and their potential to remain dangerous many years after a conflict has ended, harming civilians and the economy. With pressure from a number of campaign groups organised through the International Campaign to Ban Landmines, a global movement to prohibit their use led to the 1997 Convention on the Prohibition of the Use, Stockpiling, Production and Transfer of Anti-Personnel Mines and on their Destruction, also known as the Ottawa Treaty. To date, 164 nations have signed the treaty. However, China, Russia, and the United States are not signatories.

The Anti-Personnel Mine Ban Convention (also known as the Ottawa Treaty) and the Protocol on Mines, Booby-Traps and Other Devices define a mine as a "munition designed to be placed under, on or near the ground or other surface area and to be exploded by the presence, proximity or contact of a person or vehicle". Similar in function is the booby-trap, which the protocol defines as "any device or material which is designed, constructed or adapted to kill or injure and which functions unexpectedly when a person disturbs or approaches an apparently harmless object or performs an apparently safe act". Such actions might include opening a door or picking up an object. Normally, mines are mass-produced and placed in groups, while booby traps are improvised and deployed one at a time. Booby traps can also be non-explosive devices such as punji sticks. Overlapping both categories is the improvised explosive device (IED), which is "a device placed or fabricated in an improvised manner incorporating explosive material, destructive, lethal, noxious, incendiary, pyrotechnic materials or chemicals designed to destroy, disfigure, distract or harass. They may incorporate military stores, but are normally devised from non-military components." Some meet the definition of mines or booby traps and are also referred to as "improvised", "artisanal" or "locally manufactured" mines. Other types of IED are remotely activated, so are not considered mines.

Remotely delivered mines are dropped from aircraft or carried by devices such as artillery shells or rockets. Another type of remotely delivered explosive is the cluster munition, a device that releases several submunitions ("bomblets") over a large area. The use, transfer, production, and stockpiling of cluster munitions is prohibited by the international CCM treaty. If bomblets do not explode, they are referred to as unexploded ordnance (UXO), along with unexploded artillery shells and other explosive devices that were not manually placed (that is, mines and booby traps are not UXOs). Explosive remnants of war (ERW) include UXOs and abandoned explosive ordnance (AXO), devices that were never used and were left behind after a conflict.

The history of land mines can be divided into three main phases: In the ancient world, buried spikes provided many of the same functions as modern mines. Mines using gunpowder as the explosive were used from the Ming dynasty to the American Civil War. Subsequently, high explosives were developed for use in land mines.

Some fortifications in the Roman Empire were surrounded by a series of hazards buried in the ground. These included goads, one-foot-long (30 cm) pieces of wood with iron hooks on their ends; lilia (lilies, so named after their appearance), which were pits in which sharpened logs were arranged in a five-point pattern; and abatis, fallen trees with sharpened branches facing outwards. As with modern land mines, they were "victim-operated", often concealed, and complicated attempts by the enemy to remove the obstacles by making them vulnerable to projectiles such as spears. A notable use of these defenses was by Julius Caesar in the Battle of Alesia. His forces were besieging Vercingetorix, the leader of the Gauls, but Vercingetorix managed to send for reinforcements. To maintain the siege and defend against the reinforcements, Caesar formed a line of fortifications on both sides, and they played an important role in his victory. Lilies were also used by Scots against the English at the Battle of Bannockburn in 1314, and by Germans at the Battle of Passchendaele in the First World War.

A more easily deployed defense used by the Romans was the caltrop, a weapon 12–15 cm across with four sharp spikes that are oriented so that when it is thrown on the ground, one spike always points up. As with modern antipersonnel mines, caltrops are designed to disable soldiers rather than kill them; they are also more effective in stopping mounted forces, who lack the advantage of being able to carefully scrutinize each step they take (though forcing foot-mounted forces to take the time to do so has benefits in and of itself). They were used by the Jin dynasty in China at the Battle of Zhongdu to slow down the advance of Genghis Khan's army; Joan of Arc was wounded by one in the Siege of Orléans; in Japan they are known as tetsu-bishu and were used by ninjas from the fourteenth century onward. Caltrops are still strung together and used as roadblocks in some modern conflicts.