Oxide materials doped with lanthanide ions are technologically important, for example as laser materials and in lighting applications. Here the wet-chemical synthesis of lanthanide-doped nanomaterials, which may eventually find applications in new optoelectronic devices, is reported. It is shown that lanthanide-doped LaPO4 nanomaterials can be prepared in the high-temperature monazite phase in two morphologies—particles and fibers—via a low-temperature synthesis. The symmetry of the main dopant site was determined from the Eu3+ emission to be the same as in bulk LaPO4.