Lanthanum is a chemical element with the symbol La and atomic number 57. Lanthanum is a silvery white metallic element that belongs to group 3 of the periodic table and is the first element of the lanthanide series. It is found in some rare-earth minerals, usually in combination with cerium and other rare earth elements. Lanthanum is a malleable, ductile, and soft metal that oxidizes rapidly when exposed to air. It is produced from the minerals monazite and bastnäsite using a complex multistage extraction process. Lanthanum compounds have numerous applications as catalysts, additives in glass, carbon lighting for studio lighting and projection, ignition elements in lighters and torches, electron cathodes, scintillators, and others. Lanthanum carbonate (La₂(CO₃)₃) was approved as a medication against renal failure.

Lanthanium of Lanthaan is een scheikundig element met symbool La en atoomnummer 57. Het is een zilverwit lanthanide.