St. Martin's Island is a small island in the northeastern part of the Bay of Bengal, about 9 km south of the tip of the Cox's Bazar-Teknaf peninsula, and forming the southernmost part of Bangladesh. It is about 8 km west of the northwest coast of Myanmar, at the mouth of the Naf River. The local name of the island is "Narical Gingira", also spelled "Narikel Jinjira/Jinjera", means 'Coconut Island' in Bengali. It is the only coral island in Bangladesh.

Most of the island's 5500 inhabitants live primarily from fishing. Besides, the other staple crops are rice and coconut. Being very common in the island, Algae is collected, then dried and finally exported to Myanmar. Between October and April, the fishermen from neighbouring areas bring their caught fishes to the island's temporary wholesale market. As the centre and the south are mainly farmland and makeshift huts, most of the strenuous things are around the far north of the island.

St. Martin's Island has become a popular tourist spot. Currently, five shipping liners run daily trips to the island, including Shahid Sher Niabat, L T Kutubdia, Eagle, Keary Cruise & Dine and Keary-Sindbad. Tourists can book their trip either from Chittagong or from Cox's Bazar. The surrounding coral reef of the island has an extension named Chera Dwip. A small bush is there, which is the only green part of Chera Dwip, enhancing the beauty of this island. People do not live on this part of the island, so it is advisable for the tourists to go there early and come back by afternoon.