Holmium (Ho) is a chemical element with atomic number 67. It is one of the rare earth metals. It was discovered by Swedish chemist Per Teodor Cleve, and is named after his home town, Stockholm, which is called Holmia in Latin.

The only naturally occurring holmium isotope is ¹⁶⁵Ho, with 67 protons and 98 neutrons.

Holmium has a very high magnetic strength, and notably IBM declared in 2017 that they had managed to store data on a single Holmium atom. Holmium could potentially play a major role in future quantum computers.