A study on indigenous diatoms was carried out at 71 sites during the period from April 1999 to August 2014 in marine and fresh water in Korea. Forty species of diatoms are new to Korea and they are divided into three classes, six subclasses, 13 orders, 19 families, and 28 genera. The nomenclatures, references, dimensions, specimens examined, local habitat, distribution in Korea, and photograph are reported here. The 40 species found in marine and fresh water showed speciesspecific habitats.