According to the Völuspá, Svartalfheim is a place inhabited by dwarves in Norse Mythology.
Its treatment as a unique world in Norse cosmology is dubious, since in some manuscripts of the Prosaic Edda (by Snorri Sturluson) it is related to Nidavellir, realm of the dark elves and, by all accounts, of the dwarves.
Niðavellir has often been interpreted as one of the Nine Worlds of the giant tree Yggdrasil. The problem is that both Nidavellir and Svartalfheim are mentioned, and it is unclear whether the sixth world is a dwarven world or a dark elven one.
The dwarven world is mentioned in Snorri Sturluson's Prose Edda as Svartálfaheimr.