Nickel(II) perchlorate is a collection of inorganic compounds with the chemical formula of Ni(ClO4)2(H2O)x.

Two hydrates have been characterized by X-ray crystallography: the hexahydrate[4][5] and the octahydrate.

[6] Several other hydrates are mentioned including the pentahydrate, which is claimed to crystallize at room temperature, the nonahydrate, which is claimed to crystallize at −21.3 °C, a tetrahydrate, and a monohydrate.

[7] The yellow anhydrous product is obtained by treating nickel(II) chloride with chlorine trioxide.

As deduced by X-ray crystallography, Ni resides in a distorted octahedral environment and the perchlorate ligands bridge between the Ni(II) centers.