The melting reaction of Ir with Bi and BiBr₃ yields black, lustrous, air insensitive crystals of the subbromide Bi₃₄Ir₃Br₃₇. The triclinic crystal structure (space group P1, a = b = 1303.4(2) pm, c = 1647.4(4) pm, α = β 90°, γ = 120°, V = 2423.7 × 10⁶ pm³) deceives pseudo symmetry with respect to the rhombohedral space group R 3, which results in multiply twinned crystals. The structure can formally be subdivided in four new types of ionic groups: (a) cuboctahedral [IrBi₆Br₁₂]^- clusters, (b) [IrBi₆Br₁₃]^2- clusters with an additional Br atom, (c) Bi₅⁺ square pyramids, and (d) distorted Bi₆²⁺ octahedra. The compound shows a range of homogeneity due to variable contributions of the different clusters.