A rare element of atomic number 67 said to be contained in gadolinite. Chemical symbol Ho. Atomic weight 164.93. Valence +3. It was detected by spectral absorption bands in 1878 by the Delafontaine and Soret, who called it "Element X". Later the Swedish chemist Cleve independently discovered it in erbia, and named it after his native city Stockholm. The first preparation of pure Holmia, the yellow oxide, was not made until 1911.

a trivalent metallic element of the rare earth group; occurs together with yttrium; forms highly magnetic compounds

Holmium (IPA: ) is a chemical element in the periodic table that has the symbol Ho and atomic number 67. Part of the lanthanide series, holmium is a relatively soft and malleable silvery-white metallic element, which is stable in dry air at room temperature. A rare earth metal, it is found in the minerals monazite and gadolinite.