Holmium takes its name from Holmia, the Latin designation for Stockholm, Sweden, the home city of one of its co-discoverers.

It was identified in 1878 by Swiss chemists Marc Delafontaine and Jacques-Louis Soret, and independently by Swedish chemist Per Teodor Cleve, who is generally given primary credit for the discovery.

Holmium has atomic number 67 and the chemical symbol Ho. It is a member of the lanthanide series and is classified as a rare earth element. It is a soft, silvery-white metal that remains relatively stable in dry air at room temperature.

Among all naturally occurring elements, holmium has the highest magnetic moment, a property that makes it valuable in certain magnetic applications.

It is used in nuclear reactor control rods for its efficient neutron absorption. It also appears in solid-state lasers, particularly holmium-doped yttrium aluminum garnet lasers, known as Ho:YAG lasers, which are used in medical procedures including kidney stone removal and prostate surgery.

Holmium oxide imparts a yellow or reddish-brown color to glass, and holmium solutions display sharp, well-defined absorption bands that make them useful for calibrating spectrophotometers. Like other lanthanides, holmium has no established biological role and is considered to have low to moderate toxicity.

Holmium holds an outright record for the highest magnetic moment of any element found in nature. If the periodic table gave awards for magnetic personality, holmium would collect it unopposed.