The present checklist of diatoms has been carried out to assess and prepare an inventory of the diatom diversity in India. It covers all possible habitats, e.g. freshwater, marine, brackish water and terrestrial ecosystem. The checklist deals with a taxonomic treatment of 2777 diatom taxa which are recorded and published so far till 2017, including 2021 species and 756 infraspecific taxa belong to 269 genera, 84 families and 42 orders under 3 classes. Majority of diatom taxa have been reported from freshwater habitats (1819) followed by marine and brackish water (1365), thermal springs (170) and terrestrial (112).