Magma chambers are underground chambers that are full or partially full of molten rock. These chambers may exist beneath volcanoes or lava fountains. During volcanic eruption, the volcano and surrounding earth may collapse into the magma chamber, creating a caldera. In fantasy worlds, magma chambers may be the sites of evil lairs or evil temples.

Most of the well known magma chambers on Earth are between 1 and 10 km below the surface, but it is difficult to know if more lay below that.