Andaman Sea, northeastern arm of the Indian Ocean, bounded on the west by the Andaman and Nicobar Islands; on the north by Myanmar (formerly known as Burma); on the east by Myanmar, Thailand, and Malaysia; and on the south by Sumatra, an island that is part of Indonesia. It is linked to the South China Sea by the Strait of Malacca, and receives the Irrawaddy, Sittang, and Salween rivers. Area, 565,000 sq km (218,000 sq mi).