Abstract <p>Alunite-group minerals from various post-volcanic occurrences within the Kuril-Kamchatka suprasubduction zone, related to Alaid, Bolshoy Semiachik, Mutnovsky and Shiveluch volcanoes and Evevpenta and Vasilevo epithermal gold-silver ore occurrences, have been characterized by the combination of analytical techniques: electron-probe microanalysis, powder X-ray diffraction, and Raman spectroscopy. As a result, jarosite, alunite, natrojarosite, natroalunite and hydroniumjarosite have been found, among which natroalunite and jarosite being the most widespread. These minerals show strong genetic relation to K- and Na-feldspar, pyrite, and hematite. By chemical composition, they show a wide range of ratios for monovalent cations K/Ʃ<i>M</i>⁺. Regarding trivalent cations or Fe/(Fe + Al) ratio, both Fe³⁺- and Al-members are observed as well as rare varieties with intermediate Fe/(Fe + Al) ratios as 0.00–0.32 and 0.72–1.00. The alunite-group minerals from Shiveluch volcano contain Mg impurity up to 0.2 <i>apfu</i>, which is associated with the high Mg content of the host volcanic rocks (dacites and tephra). In individual samples Ca and P impurity is observed, substitution occurs according to the scheme <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\({\text{SO}}_{4}^{{2 - }}\)</EquationSource> <!--VolSei2660016Kupchinenko-m1--> </InlineEquation> + <i>A</i>⁺ ⇔ <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\({\text{PO}}_{4}^{{3 - }}\)</EquationSource> <!--VolSei2660016Kupchinenko-m2--> </InlineEquation> + <i>A</i>²⁺. For the first time for the alunite-group of the Kuril-Kamchatka zone, an admixture of hydroxonium (H₃O)⁺ in the position of a monovalent cation was determined by Raman spectroscopy.</p>