Arabian Sea, a broad arm of the Indian Ocean. It lies between the Indian and Arabian peninsulas. The sea is about 1,900 miles (3,100 km) east-west and 1,250 miles (2,000 km) north-south. Chief inlets of the Arabian Sea are the Gulf of Aden, leading to the Red Sea and Suez Canal, and the Gulf of Oman, leading to the Persian Gulf. Busy ports include Karachi, Aden, and Bombay. The Indus is the only major river emptying into the sea.