The　present　work　investigates　the　solubility　of　dipotassium　and　monopotassium　phosphate　in　near-　and　supercritical　water.　The　highest　solubilities　exceeded　100　mmol　kg−1　at　633.15　K　and　30　MPa,　the　lowest　temperature　and　highest　pressure　conditions　examined,　while　at　723.15　K　and　19　MPa,　the　lowest　solubilities　were　observed　for　approximately　0.2　mmol　kg−1and　0.001　mmol　kg−1.　For　potassium　phosphates,　increasing　density　and　decreasing　temperature　monotonically　increased　their　solubility.　Three　semi-empirical　models　were　employed　to　correlate　the　measured　solubility　data.　Enthalpy　model　and　ionization　model　were　demonstrated　to　provide　the　highest　accuracies　for　correlating　the　experimental　solubility　of　di-　and　monopotassium　phosphate,　respectively.　The　chemical　equilibrium　reactions　facilitating　the　dissolution　and　precipitation　of　potassium　phosphates　were　assessed　by　theoretical　calculations　via　R-HKF　equations　of　state.　Calculations　by　the　R-HKF　EOS　indicated　that　precipitation　was　thermodynamically　favored　under　all　conditions,　however,　increasing　temperature　and　water　density　promoted　the　dissolution　and　hydrolysis　of　potassium　phosphates.　©　2021　Elsevier　B.V.