The Persian Gulf is an inland Mediterranean sea in Western Asia that is an extension of the Indian Ocean from the Gulf of Oman through to the Strait of Hormuz. It is situated between Iran to the north-east and Bahrain, Iran, Iraq, Kuwait, Oman, Qatar, Saudi Arabia, and the United Arab Emirates on the Arabian Peninsula to the south-west, the Shatt al-Arab river delta constitutes its north-west shoreline. There are also several small islands located within the Persian Gulf.

Geographically the largest island in the Gulf is Qeshm Island, belonging to Iran and located in the Strait of Hormuz, other significant islands include: Greater Tunb, Lesser Tunb and Kish which are also administered by Iran; Bubiyan which belongs to Kuwait; Tarout, a territory of Saudi Arabia; and Dalma administered by the UAE. There has also been the recent addition of artificial islands that have been created by Arab states such as the UAE for commercial reasons or as tourist resorts. Despite their small size, they often have a detrimental impact on the mangrove habitats that they are built upon, causing unpredictable environmental issues.

The Persian Gulf has a surface area of roughly 251,000 square kilometres, its length is 989 kilometres and it is about 56 kilometres wide at its narrowest, in the Strait of Hormuz. The average depth of the Gulf is 50 metres and it is overall very shallow, with a maximum depth of 90 metres.

The Persian Gulf is geologically very young, as it was formed approximately 15,000 years ago. Due to the Gulf’s isolation from the international waters, with only the narrow Strait of Hormuz connecting it to the ocean, the wildlife of the waters is diverse and is host to some of the most spectacular marine fauna and flora, from a variety of corals to Dugongs, Dolphins and Finless Porpoises. The Persian Gulf is also the habitat for over 700 species of fish, most of which are native to the region and depend on the coral reef for their survival. There are also many migratory and local birds to be found in the Gulf. Unfortunately the ecology of the region is under threat from industrialisation and oil spills, with many species near extinction.

The Persian Gulf and the coastal areas around it are the world's largest single source of crude oil, and oil related industries dominate the area and the world's largest offshore oilfield, the Safaniya Oil Field is found here. The strategic location of the Gulf has also made it an ideal setting for human settlements over time and today many there are many major Middle Eastern cities in to be found in the region.