The crystal structure of ZnBr2 is tetragonal, space group I41/acd, a = 11.389(4), c = 21.773(9) Å, V = 2826(3) A3, μ = 308.2 cm−1. Dm = 4.208, Z = 32, Dx = 4.233 Mg m−3. The structure was determined from 146 independent observed [F > 2σ(F)] reflections to an R value of 0.074. The bromide ions are arranged in an fcc array with Zn atoms filling in 1/4 of the tetrahedral sites. This results in the formation of ‘super-tetrahedral’ groups of Zn4Br6Br4/2, which again interconnect to give a three-dimensional network. These groups are similar to those of P4O10, hexamethylenetetramine, [N4(CH2)6], and the large ‘cage’, Zn4S6/2S4/4, present in the zinc blende structure. However, the cage groups in ZnBr2 have point group [unk] in this space group and they are only slightly deviated from [unk]3m, the point group for idealized cages. The mean Zn – Br distance is 2.42(1) Å, and the mean Br – Zn – Br angle is 109(3)°. All the Br atoms are 2-coordinated, with Zn – Br – Zn angles ranging from a mean value of 105.3(3) for intracage bonds to 107.9(5)° for intercage connections. The ZnBr2 structure is related to those of HgI2, Be3P2 and Cd3As2 in a very interesting way.