Quasi-chemical theory and electronic structure results on inner-sphere H(H2O)n+ clusters are used to discussthe absolute hydration free energy of H+(aq). It is noted that this quantity is not thermodynamically measurable,and this leads to some relative misalignment of available tables of absolute hydration free energies of ions inwater. The simplest quasi-chemical model produces a reasonable quantitative result in the range of −256 to−251 kcal/mol. The primitive concepts on which the model is based naturally identify the Zundel cationH5O2+ as the principal chemical structure contributing to this hydration free energy. The specific participationof an Eigen cation H9O4+ is not required in this model because the definition of that structure depends onouter-sphere arrangements, and a crude dielectric continuum model is here used for outer-sphere contributions.