The 1st comprehensive checklist of Korean marine harpacticoid copepods is provided here with the purpose of being more informative compared to other conventional checklists. The checklist includes data from both marine and brackish-water habitats, along with reports on the occurrence of a few common planktonic harpacticoids. The checklist comprises 88 taxa of species and subspecies belonging to 23 families and 58 genera, encompassing planktonic, free-living benthic, and invertebrate-associated benthic forms. Details of corresponding ecological data for the listed species are provided, including habitats, substratum, salinity range, lifestyle, and size range. The most speciose families are the Miraciidae and Thalestridae (11 species each), followed by the Harpacticidae and Porcellidiidae (8 species each), which were primarily collected from littoral algae. A historical review focusing on newly reported harpacticoid species from Korean marine and brackish-water habitats is presented as an indicator of scientific efforts in harpacticoid taxonomy in Korea. Eighty-eight Korean harpacticoids are categorized according to habitat type and life form, and their distributional characteristics are further discussed. Comparisons are also made with existing checklists from other regions across the world of comparable biogeographical coverage. Finally, the limitations, significance, and role of checklists are briefly discussed.