Majuli is situated in the upper reaches of the Brahmaputra River in Assam. It is formed by the Brahmaputra River to the south and the Kherkutia Xuti, joined by the Subansiri River, to the north. The island represents a complex fluvial geomorphology, characterized by active floodplains, countless *beels* (wetlands), and shifting sandbars known locally as *chars*.
Ecologically, the island is a vibrant wetland ecosystem. It acts as a crucial habitat for rare and endangered avifauna, including migratory birds like the greater adjutant stork, pelicans, and the Siberian crane, which visit during the winter months. The flora is typical of the Brahmaputra valley, featuring riparian forests, elephant grass, and expansive agricultural tracts. The island's geography is highly dynamic, with its boundaries perpetually reshaped by the monsoon floods.