Great Nicobar is the largest of the Nicobar Islands of India, it is also the southermost point of India.
The island covers 1045 km² but is sparsely inhabited.
The island was severely affected by the 2004 Indian Ocean earthquake tsunami with many deaths, and was cut off from all outside contact for more than a day.

The island has several rivers, including the Alexandra, Amrit Kaur, Dogmar and Galathea. Virtually all rivers flow in a southern or southwesterly direction, which is indicative of the general slope of the terrain across the island.
There are undulating hills throughout the island, with the main range running in a north-south orientation. Mount Thuillier, which is part of this range, has the highest elevation of any point in the Nicobars, at 642 m above sea level. Indira Point was submerged in the 2004 tsunami.