Hafnium (Hf) is a chemical element with atomic number 72. There are several naturally occurring hafnium isotopes but ¹⁸²Hf, with 72 protons and 110 neutrons, is the most common one.

Hafnium is used in nuclear reactor control rods, where it absorbs neutrons, and also in alloys with other metals to make them more resistant to corrosion.