The first examples of dimeric, di-Pt^II-containing heteropolytungstates are reported. The two isomeric di-platinum(II)-containing 22-tungsto-2-phosphates [anti-Pt^II₂(α-PW₁₁O₃₉)₂]^10- (1 a) and [syn-Pt^II₂(α-PW₁₁O₃₉)₂]^10- (2 a) were synthesized in aqueous pH 3.5 medium using one-pot procedures. Polyanions 1 a and 2 a contain a core comprising two face-on PtO₄ units, with a Pt⋯Pt distance of 2.9-3 Å. Both polyanions were investigated by single-crystal XRD, IR, TGA, UV/Vis, ³¹P NMR, ESI-MS, CID-MS/MS, electrochemistry, and DFT. On the basis of DFT and electrochemistry, we demonstrated that the {Pt₂^II} moiety in 1 a and 2 a can undergo fully reversible two-electron oxidation to {Pt₂^III}, accompanied by formation of a single Pt-Pt bond. Hence we have discovered the novel subclass of Pt^III-containing heteropolytungstates.