Studies on aquatic insect fauna were carried out at the largest river island of the world, Majuli during 2016-17. Seasonal surveys conducted during pre monsoon, monsoon, post monsoon and winter covering 60 sampling sites revealed the occurrence of a wide array of aquatic insects. Altogether 48 aquatic insect species belonging to 6 orders and 20 families were recorded. At order level, Odonata was found to be the most dominant order (47.92%) with the highest numbers of species (23) followed by Coleoptera and Hemiptera (18.75% abundance with 9 species each). Comparatively, only few aquatic insect species were registered under Ephemeroptera (6.25%, 3), Tricoptera (4.17%, 2) and Diptera (4.17%, 2).