The Indian Ocean is the third largest ocean in the world and has a surface area of 70,560,000 square kilometres, accounting for approximately 20% of the water on the Earth's surface. The Indian Ocean is bounded by Asia to the north, Africa to the west, Australia to the east and by the Southern Ocean or Antarctica to the south. The entire Indian Ocean is found in the Eastern Hemisphere and the centre of the Eastern Hemisphere is located in this ocean.

The seas of the Indian Ocean include: the Andaman Sea, the Bay of Bengal, the Laccadive Sea, Gulf of Mannar, the Arabian Sea, the Gulf of Aden, the Gulf of Kutch, the Gulf of Khambat, the Gulf of Oman, the Persian Gulf, the Gulf of Bahrain, the Red Sea, the Gulf of Aqaba, the Gulf of Tadjoura, the Mozambique Channel, the Gulf of Carpentaria and the Great Australian Bight. Its major choke points include: the Palk Strait, the Strait of Hormuz, the Bab el Mandeb Strait, and the Indonesian Seaway comprising the Strait of Malacca, the Sunda Strait and the Torres Strait. The Indian Ocean is artificially connected to the Mediterranean Sea via the Suez Canal, which is accessible by the Red Sea.

The continental shelves of the ocean are narrow, averaging 200 kilometres in width, with the exception of Australia's western coast, where the shelf width exceeds 1,000 kilometres. The Indian Ocean has an average depth of 3,890 metres with its deepest point being Diamantina Deep in Diamantina Trench, at 8,047 metres.

Due to the strong monsoon winds, the western Indian Ocean is one of the tropical oceans that is host one of the largest concentrations of phytoplankton blooms in the summer months. These phytoplankton blooms sustain the marine ecosystem, as the base of the marine food chain. The Indian Ocean provides the second largest share of the most economically valuable tuna catch which are of increasing importance to the bordering countries for exportation and domestic consumption. Fishing fleets from further afield like Russia, Japan, South Korea, and Taiwan also exploit the Indian Ocean, primarily for shrimp and tuna.

Unfortunately research suggests that rising ocean temperatures are having a negative impact on the marine ecosystem. Studies have indicated that during the past six decades there has been a decline of up to 20% of the marine phytoplankton in the Indian Ocean. Ocean warming and the advent of industrial fisheries has also led to a reduction in the tuna catch rates during the past half century. Other marine species that are endangered include the Dugong, Seals, Turtles, and Whales. However, in 2016, researchers from Southampton University in the UK identified six new animal species in hydrothermal vents beneath the Indian Ocean, which included a "Hoff" crab, a "giant peltospirid" snail, a whelk-like snail, a scaleworm, a limpet, and a polychaete worm.

The Indian Ocean is also the location of major sea routes that connect the Middle East, Africa, and East Asia with Europe and the Americas. It is estimated that 40% of the world's offshore oil production originates from the Indian Ocean, with heavy traffic in petroleum and petroleum products coming from the oil fields of the Persian Gulf and Indonesia.