The purpose of this application is to conserve the name Johnstonia Quatrefages, 1866 for a genus of marine polychaetes (family MALDANIDAE). Quatrefages had earlier (1849) applied this name in a different taxonomic sense to an indeterminate species in the NEREIDAE. The suppression of the unused senior homonym is proposed, as is the formal rejection of the junior homonyms Johnstonia Fuhrmann, 1920 (Cestoda) and Johnstonia Basir, 1956 (Nematoda).