We report here the selective synthesis of air-stable phase-pure pyrite FeS2 nanocubes, spheroidal nanocrystals, and microspheres by solvent-induced oriented attachment (OA). It was found that the solvents could control the OA process and thus the morphologies of the products. Solvent exchange experiments and detailed Raman analysis revealed that 1-octanol contributed to the long-term stability of these pyrite nanomaterials.