The first barium sodide, with stoichiometry Ba2+(H(5)Azacryptand[2.2.2](-))Na-.2MeNH(2), was synthesized by the reaction of Ba, Na, and H(6)Azacryptand[2.2.2] in NH3-MeNH2 solution. It was characterized by X-ray crystallography, Na-23 MAS NMR, hydrogen evolution, DSC, optical spectroscopy, and magnetic susceptibility. This is the first sodide in which the sodium anions form (Na-2)(2-) dimers. Previous theoretical predictions were verified by a calculation of the potential energy curve for the dimer in the field of the surrounding charges, whose positions were determined from the crystal structure.