The reaction of Na2WO4 and SeO2 under moderately acidic conditions yielded a novel 39-tungsto-6-selenite, [(Se2W12O46(WO(H2O))3](24-) (1), isolated as Na24[H6Se6W39O144]·74H2O. The macrocyclic polyanion consists of three {Se2W12} fragments connected via three trans-{WO(H2O)}(4+) groups. The same {Se2W12} building block is present in the structure of [(Se2W12O46)2{Mn2Cl(H2O)2}{Mn(H2O)2}2(SeO)2](13-) (2), which was obtained from the same reagents in the presence of MnCl2. The compounds were characterized by single-crystal X-ray diffraction, (77)Se NMR, Fourier transform infrared, and Raman spectroscopy.