The Arabian Sea lies between the Arabian Peninsula and India. It is underlain by the abyssal plain of the Arabian Basin. This oceanic part of the Indian Plate is bounded to the west by the Owen Fracture zone, a transform boundary with the Arabian Plate, and to the south by the Carlsberg Ridge, a mid-ocean spreading ridge where India and Africa are diverging.
To the west lies the Gulf of Aden, a precursor to the Red Sea rift, with a well-established spreading ridge. The continental shelf of the Indian subcontinent to the east is broad in places, and the depositional fan of the Indus River extends some distance across the deep floor of the basin. Mumbai, formerly known as Bombay, is the largest port on the Indian coast.