We show computational evidence that ground-state moderately strong hydroxyarenes (Ar-OH, pK(a) similar to 0) dissociate by forming an ion-pair intermediate that lives for 3-5 ps. The concentration of this intermediate is approximately 2 times smaller than that of the un-ionized acid at pH similar to 0.6 and is characterized by average C-O bond lengths (1.30 angstrom) that are intermediate between those of un-ionized (1.29 angstrom) and fully dissociated (1.34 angstrom) species. During the lifetime of the ion-pair intermediate the excess proton fluctuates between the oxygen atom of the phenolic moiety and those of water molecules in the first and second solvation shells on a subpicosecond time scale.(similar to 100-300 fs).