Polycrystalline samples of the phosphide oxides RE2AuP2O (RE = La, Ce, Pr, Nd) were obtained from mixtures of the rare earth elements, binary rare earth oxides, gold powder, and red phosphorus in sealed silica tubes. Small single crystals were grown in NaCl/KCl fluxes. The samples were studied by powder X-ray diffraction, and the structures were refined from single crystal diffractometer data: La2AuP2O type, space group C2/m, a = 1515.2(4), b = 424.63(8), c = 999.2(2) pm, beta = 130.90(2)degrees, wR2 = 0.0410, 1050 F-2 values for Ce2AuP2O, and a = 1503.6(4), b = 422.77(8), c = 993.0(2) pm, beta = 130.88(2)degrees, wR2 = 0.0401, 1037 F-2 values for Pr2AuP2O, and a = 1501.87(5), b = 420.85(5), c = 990.3(3) pm, beta = 131.12(1)degrees, wR2 = 0.0944, 1143 F-2 values for Nd2AuP2O with 38 variables per refinement. The structures are composed of [RE2O](4+) polycationic chains of cis-edge-sharing ORE4/2 tetrahedra and polyanionic strands [AuP2](4-), which contain gold in almost trigonal-planar phosphorus coordination by P3- and P24- entities. The isolated phosphorus atoms and the P-2 pairs in La2AuP2O could clearly be distinguished by P-31 solid state NMR spectroscopy and assigned on the basis of a double quantum NMR technique. Also, the two crystallographically inequivalent La sites could be distinguished by static La-139 NMR in conjunction with theoretical electric field gradient calculations. Temperature-dependent magnetic susceptibility measurements show diamagnetic behavior for La2AuP2O. Ce2AuP2O and Pr2AuP2O are Curie-Weiss paramagnets with experimental magnetic moments of 2.35 and 3.48 mu(B) per rare earth atom, respectively. Their solid state P-31 MAS NMR spectra are strongly influenced by paramagnetic interactions. Ce2AuP2O orders antiferromagnetically at 13.1(5) K and shows a metamagnetic transition at 11.5 kOe. Pr2AuP2O orders ferromagnetically at 7.0 K.