Nitrogen, one of the most abundant elements in nature, forms the highly stable N 2 molecule in its elemental state. In contrast, polynitrogen compounds comprising only nitrogen atoms are rare, and no molecular crystal made of these compounds has been prepared. Here, we predict the existence of such a molecular solid, consisting of N 8 molecules, that is metastable even at ambient pressure. In the solid state, the N 8 monomers retain the same structure and bonding pattern as those they adopt in the gas phase. The interactions that bind N 8 molecules together are weak van der Waals and electrostatic forces. The solid is, according to calculations, more stable than a previously reported polymeric nitrogen solid, including at low pressure (below 20 GPa). The structure and properties of the N 8 molecular crystal are discussed and a possible preparation strategy is suggested.