In this study, a hydrolysis model for lead, applicable to high ionic strength, is developed based on lead oxide solubilities as a function of ionic strength. Solubility measurements on lead oxide, α-PbO (tetragonal, red), mineral name litharge, as a function of ionic strength were conducted in NaClO4 solutions up to I = 0.45 mol·kg−1, in NaCl solutions up to I = 5.0 mol·kg−1, and in Na2SO4 solutions up to I = 5.4 mol·kg−1, at room temperature (22.5 ± 0.5 °C). The lead hydroxyl species considered in this work include the following, 1 $$ {\text{PbO}}\left( {\text{cr}} \right) \, + {\text{ 2H}}^{ + } \rightleftharpoons {\text{Pb}}^{ 2+ } + {\text{ H}}_{ 2} {\text{O}}\left( {\text{l}} \right) $$ 2 $$ {\text{Pb}}^{ 2+ } + {\text{ H}}_{ 2} {\text{O}}\left( {\text{l}} \right) \rightleftharpoons {\text{PbOH}}^{ + } + {\text{ H}}^{ + } $$ 3 $$ {\text{Pb}}^{ 2+ } + {\text{ 2H}}_{ 2} {\text{O}}\left( {\text{l}} \right) \rightleftharpoons {\text{Pb}}\left( {\text{OH}} \right)_{ 2} \left( {\text{aq}} \right) \, + {\text{ 2H}}^{ + } $$ 4 $$ {\text{Pb}}^{ 2+ } + {\text{ 3H}}_{ 2} {\text{O}}\left( {\text{l}} \right) \rightleftharpoons {\text{Pb(OH}})_{3}^{ - } + 3{\text{H}}^{ + } $$ The equilibrium constants for Reactions (1) and (2) were taken from literature. The equilibrium constants in base 10 logarithmic units for Reactions (3) and (4) are determined in this study as − 17.05 ± 0.10 (2σ) and − 27.99 ± 0.15 (2σ), respectively, with a set of Pitzer parameters describing the interactions with Na+, Cl−, and $$ {\text{SO}}_{4}^{2 - } .$$ In combination with the parameters from literature including those that have already been published by our group, the solution chemistry of lead in a number of media including NaCl, MgCl2, NaHCO3, Na2CO3, Na2SO4, NaClO4, and their mixtures, can be accurately described in a wide range of ionic strengths.