Single crystals of anhydrous dimercury(I) monofluorophosphate(V), Hg2PO3F (1), were obtained by cooling diluted aqueous Hg-2(NO3)(2) and (NH4)(2)PO3F solutions from 85 degreesC to room temperature. Compound 1 crystallizes with eight formula units in the orthorhombic space group Ibam (No. 72) and lattice parameters a = 9.406(2) Angstrom, b = 12.145(3) Angstrom, c = 8.567(2) Angstrom. It adopts a new structure type even though a topological relation with dimercury(l) sulfate, Hg2SO4, is established. The crystal structure of 1 (R(F-2 > 2sigma(F-2) = 0.0353) exhibits Hg-2(2+) dumbbells and discrete PO3F2- anions as single building units which are organized in a layered assembly parallel to (100). The symmetric Hg-2(2+) dumbbell shows a typical Hg-Hg distance of 2.5051(9) Angstrom, and for each Hg atom, three Hg-O distances are found, ranging from 2.327(6) to 2.476(5) Angstrom. No interactions between Hg and F atoms are realized. The latter is exclusively bonded to the phosphorus atom at a distance d(P-F) = 1.568(8) Angstrom which is considerably longer than the P-O distances with a mean of 1.515 Angstrom. Compound 1 was further characterized by vibrational spectroscopy (Raman and IR) in the spectral range between 4000 and 50 cm(-1), thermal analysis (TG, DSC) Lip to 650 degreesC which revealed Hg-2(P2O7) and Hg-3(PO4)(2) as thermal decomposition products, and F-19 and P-31 solid-state NMR spectroscopy. The value for the P-F coupling constant in 1 is J(PF) = -1072 Hz at 20 degreesC. The absolute sign of J(PF) is negative.