The Elephant’s Foot is the nickname given to a large mass of corium formed during the Chernobyl disaster in April 1986 and presently located in a steam distribution corridor underneath the remains of the reactor. It is currently an extremely deadly radioactive compound, yet its danger has decreased with the decay of its radioactive components.

The largest known amounts of corium were formed during the Chernobyl disaster.[15] The molten mass of reactor core dripped under the reactor vessel and now is solidified in forms of stalactites, stalagmites, and lava flows; the best known formation is the "Elephant's Foot," located under the bottom of the reactor in a Steam Distribution Corridor

Corium, also called fuel containing material (FCM) or lava-like fuel containing material (LFCM), is a lava-like material created in the core of a nuclear reactor during a meltdown accident.