A battering ram is a siege engine that originated in ancient times and was designed to break open the masonry walls of fortifications or splinter their wooden gates. In its simplest form, a battering ram is just a large, heavy log carried by several people and propelled with force against an obstacle; the ram would be sufficient to damage the target if the log were massive enough and/or it were moved quickly enough (that is, if it had enough momentum). Later rams encased the log in an arrow-proof, fire-resistant canopy mounted on wheels. Inside the canopy, the log was swung from suspensory chains or ropes.

Rams proved effective weapons of war because at the time wall-building materials such as stone and brick were weak in tension, and therefore prone to cracking when impacted with force. With repeated blows, the cracks would grow steadily until a hole was created. Eventually, a breach would appear in the fabric of the wall, enabling armed attackers to force their way through the gap and engage the inhabitants of the citadel.

The introduction in the later Middle Ages of siege cannons, which harnessed the explosive power of gunpowder to propel weighty stone or iron balls against fortified obstacles, spelled the end of battering rams and other traditional siege weapons. Smaller, hand-held versions of battering rams are still used today by law enforcement officers and military personnel to break open locked doors.

A capped ram is a battering ram that has an accessory at the head (usually made of iron or steel and sometimes punningly shaped into the head and horns of an ovine ram) to do more damage to a building. It was much more effective at destroying enemy walls and buildings than an uncapped ram but was heavier to carry.