In the course of hydrothermal synthesis of lanthanum vanadates, zircon-type LaVO 4 and LaV 3 O 9 have been obtained and structurally characterized. The former is a metastable phase, and the latter is a new compound. Single-crystal X-ray diffractometry confirmed the zircon-type structure for LaVO 4 : I4 1 /amd with a=7.4578(7) Å, c=6.5417(9) Å, and Z=4; R=0.020 and R w =0.025 for 276 reflections with I>3σ(I). The structure consists of isolated VO 4 tetrahedra which surround the La atom to form a LaO 8 dodecahedron. LaV 3 O 9 adopts the monoclinic system: P2 1 /m with a=4.949(2) Å, b=9.547(3) Å, c=7.411(2) Å, β=100.76(2)°, and Z=2; R=0.035 and R w =0.042 for 1868 reflections with I>3σ(I). The structure adopts a chain-type one consisting of a V 3 O 9 chain along [010] which is made up of edge-sharing VO 5 trigonal-bipyramid pairs and VO 4 tetrahedra. The La atom residues between the V 3 O 9 chains and is coordinated with ten oxygens. The present study demonstrates the applicability of hydrothermal method to the synthesis of new and/or metastable lanthanide vanadates.