AbstractPolybromide monoanions of the series [NAlk4][Br9] (Alk = methyl, ethyl, propyl, butyl) have been investigated. The corresponding salts were characterized by Raman spectroscopy, single‐crystal X‐ray diffraction and state‐of‐the‐art quantum‐chemical calculations. Comparisons between their crystal structures and the gas‐phase calculations have been made whereas the latter shows regular tetrahedral arrangement. Usually the nonabromides contain one central Br– anion at which all other four Br2 molecules are coordinated. The only exception is [NBu4][Br9] where also a [Br3]– unit is found.Quantum‐chemical calculations show that dispersion as well as spin‐orbit corrections alter the results only marginally and can be neglected. Conductivity measurements show a surprisingly high conductivity of these polybromide monoanions. It is found that the tetraalkylammonium nonabromide salts (alkyl = methyl, ethyl, propyl, and butyl) show decreasing conductivity as the size of the cation increases. Making thesepolybromide monoanions possible electrolytes in batteries or dye‐sensitized solar cells.