Magnesium nitrate refers to inorganic compounds with the formula Mg(NO3)2(H2O)x, where x = 6, 2, and 0.

[2] The anhydrous material is hygroscopic, quickly forming the hexahydrate upon standing in air.

Being highly water-soluble, magnesium nitrate occurs naturally only in mines and caverns as nitromagnesite (hexahydrate form).

The principal use is as a dehydrating agent in the preparation of concentrated nitric acid.

Magnesium nitrate reacts with alkali metal hydroxide to form the corresponding nitrate: Since magnesium nitrate has a high affinity for water, heating the hexahydrate does not result in the dehydration of the salt, but rather its decomposition into magnesium oxide, oxygen, and nitrogen oxides: The absorption of these nitrogen oxides in water is one possible route to synthesize nitric acid.