Mumbai Harbou (Mumbay bay or Marathi: मुंबई बंदर or Front Bay) is a natural deep-water harbor in the southern portion of the Ulhas River estuary in India. The narrower, northern part of the estuary is called Thane Creek. The harbor opens to the Arabian Sea to the south. The historical island of Elephanta is one of the six islands that lie in the harbor. It is also site of the Gateway to India swim.
Front Bay is the official name of the harbor, so named because Mumbai started as a tiny settlement facing the harbor. The waterbody behind the original settlement, forming an arc between the former Colaba island and Bombay island, up to the Malabar Hill promontory or peninsula, was similarly called Back Bay.
Front Bay is home to the Mumbai Port, which lies in the south section of the western edge of the harbor. Jawaharlal Nehru Port and Navi Mumbai lie to the east on the Konkan mainland, and the city of Mumbai lies to the west on Salsette Island. The Gateway of India with its jetty for Elephanta is the most important tourist destination, followed by the INS Vikrant maritime Museum.