Bastnäsite (or Bastnaesite) is a rare-earth carbonate-fluoride mineral. It is an important source of rare earth elements (REEs), particularly cerium, lanthanum, and neodymium. Named after its type locality, Bastnäs in Sweden, the mineral is typically associated with alkaline igneous rocks, carbonatites, and hydrothermal veins.

Bastnäsite is mined as a primary source of rare earth elements, which are critical in various high-tech and green technologies, including:

Magnets for wind turbines and electric vehicles (neodymium and praseodymium).
Catalysts in petroleum refining.
Polishing powders for glass and ceramics.
Alloys in aerospace and defense applications.