Eleven new species of tortoise beetles (Chrysomelidae: Cassidinae s.str.) are described from Madagascar: Androya borowieci sp. nov., Cassida borowieci sp. nov., C. donaldi sp. nov., C. jirka sp. nov., C. jolantae sp. nov., C. katka sp. nov., C. kuglerovae sp. nov., C. lechi sp. nov., C. matyasi sp. nov., C. sipovae sp. nov., and C. vlasta sp. nov. All species are provided with colour photographs and detailed diagnosis.