Potassium trichloridocuprate(II) is a salt with chemical formula KCuCl3, more properly [K+]2[Cu2Cl2−6].

[5] The compound occurs in nature as the bright red mineral sanguite.

These anions are arranged in columns consisting of distorted edge-sharing CuCl6 octahedra, stacked in double chains parallel to the a axis.

The columns occupy the edges and the centre of the cell's projection on the bc plane.

[1] The mineral is optically biaxial (negative), with α = 1.653, β = 1.780, γ = 1.900', 2V= 85°.