During an investigation of indigenous prokaryotic species in the Republic of Korea, 17 bacterial strains belonging to the phylum Bacteroidota and 4 strains belonging to the phylum Bacillota were isolated from freshwater environments. These isolated bacterial strains formed a robust phylogenetic clade with type strains of the closest related bacterial species, with 16S rRNA gene sequences sharing similarities of higher than 98.7%. To date, there have been no official report of these 21 isolates in the Republic of Korea. At the genus level, these unreported species were affiliated with Mucilaginibacter and Pedobacter of class Sphingobacteriia, Flavobacterium and Gillisia of class Flavobacteriia, Hymenobacter of class Cytophagia, and Paenibacillus and Planococcus of class Bacilli. These species were further examined by performing Gram staining, analyzing their colonies and cell morphologies, and determining their basic biochemical characteristics and phylogenetic positions. Detailed descriptions of the 21 previously unreported species are provided.