Addu Atoll, previously also known as Seenu Atoll , is the southernmost atoll of the Maldives. Addu Atoll, together with Fuvahmulah, located 30 km north of Addu Atoll, extend the Maldives into the Southern Hemisphere. Addu Atoll is located approximately 478 km south of Malé. Administratively, Addu Atoll is the site of Addu City, one of the two cities of Maldives. Addu City is constituted of the inhabited areas of Addu Atoll, namely the natural islands of Hulhumeedhoo, Maradhoo, Feydhoo, and Hithadhoo. (The districts of Addu City are not according to the natural islands that it constitutes of. ) In addition to the areas that are included as a part of Addu City, Addu Atoll has a number of uninhabited islands, including the island of Gan, where Gan International Airport is located.
Unlike other atolls of Maldives, Addu Atoll possesses a natural anchorage within the atoll basin, as the atoll is land-locked with large islands surrounding the atoll. This results in a natural harbor that is very calm and safe for sea vessels at all times, and is not affected by seasonal changes. The atoll possesses four channels, which lead into the inside.In the north are the Kuda Kandu and Maa Kandu in the south,the Gan Kandu and the broad Villingili Kandu is to the southeast.
There are unique features in the islands of Addu Atoll.The islands are protected from the storms and high waves of the Indian Ocean by barrier reefs. Coconut palms, the national tree, are able to grow almost everywhere on the Islands. There are small lakes, wetlands, and marshy taro fields in the islands that are unique. Also, White tern known as the "dhondheeni" by Adduans gives the Atoll a uniqueness as it is found only in Addu Atoll in Maldives.
The Addu Atoll also possesses particularly rich whale and dolphin fauna. A great diversity of species has been found there. Addu Atoll is the only area in the Maldives that was not affected by the 1998 global coral bleaching. The south of the Maldives was spared from the “too warm” major ocean currents (El Niño); the bright and healthy corals start at the top of giris and thilas (about 1 meter [3 ft] under the surface) and slope down with the reef to a depth of 30 meters (98 ft) or more.