The crystal structure of dilithium dimanganese trisulfate Li 2 Mn 2 (SO 4 ) 3 has been established by single-crystal X-ray diffraction. This compound crystallizes in the orthorhombic system (space group Pbca, Z β«Ψβ¬ 8) with cell parameters a β«Ψβ¬ 8.686(2) A > , b β«Ψβ¬ 8.792(2) A > , and c β«Ψβ¬ 24.146(4) A > . The structure was re5ned to R β«Ψβ¬ 0.035 and Rw β«Ψβ¬ 0.037 using 2622 independent re6ections. Lithium and sulfur atoms are in most regular tetrahedral oxygen coordination, manganese atoms are in slightly distorted octahedral oxygen coordination. Formally, the 3-D framework can be described, starting from the Li 2 Mg 2 (SO 4 ) 3 structure, by condensation of Sc 2 (WO 4 ) 3 -type slabs. As a result, half of the LiO 4 and MnO 6 polyhedra share an edge, forming Li 2 O 6 and Mn 2 O 10 dimeric entities. Below T N β«Ψβ¬ 10 K, the magnetic susceptibility evolution is characteristic of a long-range antiferromagnetic order. In the high-temperature region, the susceptibility follows a Curie+Weiss law with C β«Ψβ¬ 8.51 cm 3 K mol Ψ1 and β«Ψβ¬ Ψ19 K. In a Mn 2 O 10 bioctahedron the Mn 2Ψ cations are indeed antiferromagnetically coupled with an interaction parameter J β«Ψβ¬ Ψ6.5 cm Ψ1 .