The polychalcogenide compound AuCuSe4 crystallizes in the monoclinic space group P2(1)/m. with a = 4.318(2) Angstrom, b = 7.447(1) Angstrom, c = 8.099(1) Angstrom, beta = 93.33(2)degrees, and Z = 2. The structure of AuCuSe4 is a unique three-dimensional framework assembled from formally Au3+ and Cu+ ions and Se-3(2-) and Se2- fragments. Conceptually, the framework is composed of one-dimensional [Au(Se-3)Se](n)(n-) chains linked by Cu+ atoms. The An atoms adopt a square plan ar geometry, while Cu atoms adopt a severely distorted tetrahedral geometry. The Se32- ligand in this structure shows an unprecedented ligation mode using both its terminal and internal selenium atoms. The material is a p-type narrow gap semiconductor with a band gap of similar to0.52 eV.