St. Martin's Island is a small island (about 8 square kilometres) in the northeast of the Bay of Bengal. It is about 9 km south of the tip of the Cox's Bazar-Teknaf peninsula, and is the southernmost part of Bangladesh. There is a small connected island that is separated at high tide, called Chhera Island. It is about 8 km west of the northwest coast of Myanmar, at the mouth of the Naf River.