a gulf in the northern Andaman Sea of the Indian Ocean, off the coast of Burma. The Gulf of Martaban is about 150 km long, about 220 km wide at the point of entry, and up to 20 m deep. The gulf has semidiurnal tides of 7.2 m. Rangoon, an important ocean and river port and the capital of Burma, is situated at the mouth of the Rangoon River, which empties into the Gulf of Martaban.