Single-crystalline nanobelts and nanorings of Na2V6O16 center dot 3H(2)O structures have been facilely synthesized through a direct hydrothermal reaction between NaVO3 and H3PO4, without the addition of any harmful solvents or surfactants. The analytical techniques of scanning electron microscopy, transmission electron microscopy (TEM), powder X-ray diffraction, thermogravimetric analysis, energy-dispersive X-ray spectroscopy, Fourier transform infrared, high-resolution TEM, and selected-area electron diffraction have been used to characterize the morphology, composition, and structure of the synthesized products. The Na2V6O16 center dot 3H(2)O nanobelts are up to several hundreds of micrometers in length and 100-300 nm in thickness, and for nanorings, the diameters are 4.5-6.5 mu m. H3PO4 plays a key role in maintaining the pH of the solution as well as producing PO43- ions in solution. The chemical reactions and a possible growth mechanism involved in the formation of Na2V6O16 center dot 3H(2)O nanobelts and nanorings are briefly discussed.