Calcium iodide (chemical formula CaI2) is the ionic compound of calcium and iodine.

This colourless deliquescent solid is a salt that is highly soluble in water.

Its properties are similar to those for related salts, such as calcium chloride.

[1] It is also used in cat food as a source of iodine.

Henri Moissan first isolated pure calcium in 1898 by reducing calcium iodide with pure sodium metal:[3] Calcium iodide can be formed by treating calcium carbonate, calcium oxide, or calcium hydroxide with hydroiodic acid:[4] Calcium iodide slowly reacts with oxygen and carbon dioxide in the air, liberating iodine, which is responsible for the faint yellow color of impure samples.