This is a critical review and compilation of the observed and predicted spectroscopic data on the molecule N2 and its ions N2−, N2+, N22+, and the molecule N3. Each electronic band system is discussed in detail, and tables of band origins and heads are given. In addition to the gas phase electronic, electron and Raman spectra, there are also examined the spectra of condensed molecular nitrogen as well as the pressure‐ and field‐induced infrared and microwave absorption. Dissociation energy of N2, predissociations, and perturbations are discussed. Potential energy curves are given, as well as radiative lifetimes, f‐values, and Franck‐Condon integrals. Molecular constants are listed for the known electronic states. Electronic structure and theoretical calculations are reviewed.