A taxonomic study on the diatoms from the Kwang River (Kwangchun), less polluted, in S. Korea is reported. In this paper 99 taxa of Naviculaceae classified into 87 species and 12 varieties of 16 genera are described. Eighteen of these taxa are new for Korea. For ‘Navicula yuraensis’the condition for valid publication is fulfilled. Pleurosigma negoroi sp. nov. is formally described.