A stalagmite (from the Greek Σταλαγμίτης Stalagmítēs 'drop') is a type of speleothem (deposit of minerals formed by chemical precipitation) that forms on the floor of a limestone cave due to the decantation of solutions and the deposition of calcium carbonate. The corresponding formation on the ceiling of a cave is known as a stalactite. If these formations grow large enough to meet, the result is called a "Column (caving)") column or pillar.

The tallest stalagmite is found in Zhin Jin Cave, China; it measures 70 meters high.[1]​.

Similar structures can also form in lava tubes, associated with some types of staphylites, although the formation mechanism is very different. Stalactites and stalagmites can also form on concrete ceilings and floors, although their formation is much faster than in the natural environments of caves.