St. Martin's Island (সেন্ট মার্টিন্স দ্বীপ) is a small island (area only 8 km) 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.

St Martin's is the only coral island in Bangladesh, with beaches fringed with coconut palms and laid-back locals.