Mājuli or Majuli is a river island in the Brahmaputra River, Assam and in 2016, it became the first island to be made a district in India. In the 1790s, the island covered an area of 1,300 km2 (500 sq mi). It had an area of 1,255 square kilometres (485 sq mi) at the beginning of the 20th century, but having lost significantly to erosion it covers 352 square kilometres (136 sq mi) as at 2014. Majuli has shrunk as the river surrounding it has grown.

The island is formed by the Brahmaputra River in the south and the Kherkutia Xuti, an anabranch of the Brahmaputra, joined by the Subansiri River in the north. Mājuli island is accessible by ferries from the city of Jorhat. The island is about 300–400 kilometres (186–249 mi) east from the state’s largest city —Guwahati.It was formed due to course changes by the river Brahmaputra and its tributaries, mainly the Lohit. Mājuli is the abode of the Assamese neo-Vaishnavite culture.

The island was a long, narrow piece of land called Majoli (land in the middle of two parallel rivers) that had the Brahmaputra flowing in the north and the Burhidihing flowing in the south until they met at Lakhu. It was once known as Ratnapur and was the capital of the powerful Sutiya kingdom. Frequent earthquakes in the period 1661–1696 set the stage for a catastrophic flood in 1750 that continued for 15 days, which is mentioned in historical texts and reflected in folklore. As a result of this flood, part of the Brahmaputra discharged southward into what was the Burhidihing’s lower channel and Mājuli island was formed.