Nanoscale pyrite FeS2 is considered to be one of few potentially transformative materials for photovoltaics capable of bridging the cost/performance gap of solar batteries. It also holds promise for energy storage applications as the material for high-performance cathodes. Despite prospects, the synthesis of FeS2 nanostructures and diversity of their geometries has been hardly studied. Moreover, the state-of-the-art aqueous dispersions of nanoscale pyrite, which have special significance for solar energetics, are particularly disappointing due to low quality. There are no known methods to produce well-crystallized nanoparticles and other geometries of nanoscale pyrite in water or mixed aqueous solvents. Here, we describe a successful synthesis of single-phase pyrite nanoparticles with a diameter of 2-5 nm in polar solvent and aqueous dispersions. The particles display high uniformity and crystallographic purity. Moreover, the synthetic approach developed for nanoparticles was proven to be quite universal and can be modified to produce both nanowires and nanosheets, which also display high crystallinity. The diameter of the pyrite nanowires was 80-120 am with the length exceeding 5 mu m. The nanosheets displayed lateral dimensions of 100-200 nm with the thickness of 2 nm. Availability of single-phase FeS2 nanoscale aqueous dispersions is expected to stimulate further studies of these materials in green energy conversion technologies and drug delivery applications.