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"Rare earth elements" and "rare earth metals" are trivial names sometimes applied to a collection of 17 chemical elements in the periodic table, namely scandium, yttrium, and the lanthanides. The former two are included as they tend to occur with the latter in the same ore deposits. (The lanthanide promethium, which does not occur naturally on Earth, is not generally considered to be a rare earth element.)

"Earth" is an obsolete term for oxide. At the time of their discovery, earths of these elements were believed to be scarce in abundance as minerals (that is, rare). However, the term "rare earth" is now deprecated by IUPAC, as these elements are in fact relatively abundant in the Earth's crust: the most abundant, cerium, at 60 parts per million, is the 25th most abundant in the crust of any element, more common than lead, whilst even the least abundant "rare" earth element, lutetium, is 200 times more abundant than gold.

The principal economic sources of rare earths elements are the minerals bastnasite, monazite, and loparite and the lateritic ion-adsorption clays. Despite their relative abundance, however, these more difficult to mine and extract than those of other transition metals, making them relatively expensive.

For more details of the properties and uses of these elements, refer to the lanthanides article.

• Chemical element groups
• Metallic elements