The present paper documents the insect diversity associated with mangrove forest in three different localities under Sundarban Biosphere Reserve, West Bengal conducted during September 2021 to April 2022. A total of 392 insects from 7 orders, 23 families were recorded. At each site, during low tide, different types of insects were observed and were recorded. This study shows that Hymenoptera (33.93%) was the most dominant order according to total number of individuals, followed by Hemiptera (19.39%), and the least were Odonata (5.87%) and Ephemeroptera (0.51%) respectively. The Diversity of insects was highest in Locality1 (Hemnagar) and lowest in Locality3 (Canning).