Lanthanum was discovered in 1839 by C. G. Mosander in Stockholm, Sweden. Mosander partially decomposed a sample of cerium nitrate by heating and treating the resulting salt with dilute nitric acid. From the extracted solution, it was possible to isolate a new rare earth which Mosander called lantana, which means "hidden". The experimental work with the lanthanum was prolonged for the three following years, although the results remained unpublished.

For more than one century any important applications for this element were not found. The interest for lanthanum was just scientific, being limited to the investigators improving its separation techniques and purification and knowing its spectrum.

Although possessing an electronic configuration different from the one of the lanthanides, it is included in this series due to the likeness of properties that presents with these.