Mannar District is located in the north west of Sri Lanka in the Northern Province. It has an area of 1,996 square kilometres (771 sq mi) Mannar is the main town of Mannar District, Northern Province, Sri Lanka. It is governed by an Urban Council. The town is located on Mannar Island overlooking the Gulf of Mannar and is home to the historic Ketheeswaram temple. Formerly the town was renowned as a center of pearl fishing, mentioned in the 2nd-century CE Periplus of the Erythraean Sea. Mannar is known for its baobab trees and for its fort, built by the Portuguese in 1560 and taken by the Dutch in 1658 and rebuilt; its ramparts and bastions are intact, though the interior is largely destroyed. Visually, the modern town is dominated by its churches, Hindu temples and mosques. The Catholic Church has a diocese headquartered in the town. By rail the town is connected to the rest of Sri Lanka by the Mannar Line. It was occupied by LTTE during Sri Lankan Civil War between 1983 and 2009.
Mannar District is unique in its vegetation and wildlife, contrasting with rest of Sri Lanka. Mannar Island is one of the few places in Sri Lanka where baobab trees thrive. Monkeys love the fruit and hence the tree is sometimes known as the monkey-bread tree.
The dugong is a medium-sized marine mammal which is found in Mannar Bay, Nachchikuda, Jaffna island and near Adam's Bridge. IUCN conservation status is vulnerable because of over-hunting for food and accidental capture in fishing nets.
A critically endangered tarantula species known as Poecilotheria hanumavilasumica was first found from Sri Lanka in Mannar region. This was the first time that the spider was recorded from outside of India. The Vankalai Sanctuary for birds, internationally recognized as an important area for wetland birds under the Ramsar Convention, is on the mainland just to the south of Mannar Island.