Both oxygen and fluorine have a partiality towards the stabilization of high oxidation states of rare earths such as Ce, Pr, and Tb. During the study of the MF‐M’F4 (M=alkaline metal; M’ rare ion) the compound Li2TbF6 was found to constitute the only representative obtained under ambient pressure of a structural type, namely α‐Li2ZrF6, known until now only through the high pressure form. Magnetic measurements were carried out over the 1.4–300 K temperature range in continuous magnetic fields up to 20 T produced by a Bitter magnet. At low temperature and in H higher than 15 T, the magnetization M was observed to be field independent and very close to the calculated Tb4+ free ion value, i.e., 7μB; on the other hand, the data do not present any departure from the Brillouin function of the pure 8S7/2 state. The reciprocal magnetic susceptibility obeys a Curie–Weiss law leading to an effective moment of 7.86μB. A very unusual behavior of the terbium ion which presents a 4+ oxidation state is concluded: to the best of our knowledge, it is the first observation of this form. The so‐found spherical 4f7 electronic configuration is the most compatible with the high coordination number of eight. Finally, the discussion within the series Li2MIVF6 compounds to understand the influence of both electronic configuration and size effects is presented.