An attempt has been made to study the phytoplankton diversity of Gharni reservoir. The Sample were collected from Gharni reservoir of Latur district. Study was undertaken during the period of June 2021 to May 2022. phytoplankton population was composed of 20 species belonging to four groups were recorded. Out of these species, 10 species of Chlorophyceae, 4 species of Cynophyceae, 3 species of Bacillariophyceae and 3 species of Euglenophyceae. Among the phytoplankton chlorophyceae was found to be dominant during study period. The maximum count of phytoplankton was recorded during the months of February to May and minimum count was recorded during the months of June to September due to high temperature and low turbidity in summer season and vice versa.