Colloidal nanoparticles of a prototype polar intermetallic compound, Au3Li, were synthesized by reacting Au nanoparticle seeds with n-butyllithium. X-ray and electron diffraction data are consistent with the L12 (Cu3Au) structure type expected for Au3Li. Composition analysis indicates a stoichiometry of approximately Au3Li0.7, which is within the reported composition range of the Au3Li phase. The Au3Li nanoparticles decompose in water to regenerate Au. The successful synthesis of Au3Li as colloidal nanoparticles demonstrates that polar intermetallic compounds containing highly electropositive elements are accessible by using low-temperature solution chemistry routes and that they are also amenable to nanostructuring.