Copper(II) selenide is an inorganic binary compound between copper and selenium, with the chemical formula CuSe.

Copper(II) selenide is produced in situ to form a protective black coating on iron or steel parts in some cold-bluing processes.

[1] Bluing solutions that operate in this manner will typically be labeled as containing selenous acid or selenium dioxide.

[2][3] It has also been investigated for use in the treatment of colon cancer.

[4] Copper selenides are the most common selenium minerals.