Persian Gulf

The Persian Gulf (Persian: خلیج فارس, /xæliːdʒ-e fɒːrs/) is a shallow, semi-enclosed body of water in western Asia, between the Iranian plateau and the Arabian Peninsula. It connects to the Gulf of Oman and the Indian Ocean through the Strait of Hormuz and narrows in the northwest toward the delta of the Arvand Rud (Shatt al-Arab). Eight states border it: Iran, Iraq, Kuwait, Saudi Arabia, Bahrain, Qatar, the United Arab Emirates, and Oman.

The Persian Gulf is one of the world’s principal energy corridors, an old maritime trading zone, and a body of water with more than 2,500 years of documented naming history. Its ecological, historical, and political importance makes it central to the study of the modern Middle East.

The Gulf covers about 251,000 square kilometers, stretches roughly 990 kilometers, and varies from around 56 kilometers wide at the Strait of Hormuz to about 340 kilometers at its broadest point. Its average depth is about 50 meters, with deeper water generally concentrated along the Iranian side. Iran has the longest coastline on the Gulf; Iraq has the shortest.

Large volumes of the region’s oil and gas trade pass through the Strait of Hormuz each day. The shared South Pars/North Dome field lies between Iran and Qatar, and the littoral states collectively account for a major share of global hydrocarbon production. For that reason alone, the Gulf remains one of the world’s most closely watched maritime regions.

Geography and Physical Features

Understanding the physical characteristics of the Persian Gulf is essential, because its shallowness, semi-enclosed nature, and extreme climate have both created its distinctive ecosystem and explain its environmental vulnerability.

Geological Formation

The Persian Gulf is a geologically young Cenozoic basin formed by the subduction of the Arabian plate beneath the Zagros mountain range. During the last major glaciation — roughly 70,000 to 17,000 years ago — the Gulf floor was a dry valley through which the Tigris, Euphrates, and Karun rivers flowed toward the Strait of Hormuz, forming a drainage system known as the “Ur-Schatt.” Recent research suggests this valley may have been a favorable habitat for early human communities, with freshwater springs and a milder climate. Much of the archaeological evidence from this period now lies submerged beneath the Gulf’s waters.

After the last ice age, sea levels gradually rose in a process known as the Flandrian Transgression. The Gulf assumed approximately its present shape around 7,000 years ago. This geological youth — measured against the deep timescales of ocean basins — explains the Gulf’s characteristic shallowness and its relatively simple bathymetric profile.

The Gulf floor is asymmetric. The Iranian coast is deeper with a steeper gradient, and a deeper channel runs along its length on the Iranian side. The Arabian coast is shallower and slopes more gently, with broader continental shelves. The maximum depth of the Gulf — approximately 90 to 110 meters — has been recorded near the Strait of Hormuz on the Iranian side.

Strait of Hormuz

The Strait of Hormuz is the sole gateway connecting the Persian Gulf to the open ocean, and this singular geographic fact makes it one of the most strategically important straits in the world.

The strait measures approximately 56 kilometers in width, but the navigable shipping lanes are far more restricted. Two traffic lanes of roughly three kilometers each handle inbound and outbound vessel movement, separated by a two-kilometer buffer zone. The enormous volume of tanker and cargo traffic means that any disruption to passage through the strait reverberates immediately across world energy markets.

Water circulation through the Strait of Hormuz follows a two-layered pattern. Dense, hypersaline water from the Persian Gulf flows outward through the depths, forming a distinctive water mass known as Persian Gulf Water that can be traced far into the Indian Ocean. Simultaneously, lighter, less saline water from the Indian Ocean enters the Gulf at the surface. This pattern is known as reverse estuarine circulation and distinguishes the Persian Gulf from most other semi-enclosed seas.

Islands of the Persian Gulf

The Persian Gulf contains dozens of islands, the most significant of which belong to Iran.

Qeshm Island is the largest island in the Persian Gulf, with an area of approximately 1,500 square kilometers. Located at the mouth of the Strait of Hormuz, it holds UNESCO Global Geopark status. Its natural attractions include mangrove forests, salt caves, and the Stars Valley geological formation. The Gouran Maritime Park-Museum on Qeshm documents the island’s seafaring heritage.

Kish Island is a free trade zone and tourist destination. After a devastating earthquake destroyed much of the port of Siraf around 970 CE, maritime trade shifted to Kish, which served for several centuries as the principal commercial hub of the Persian Gulf.

Khark Island is Iran’s most important oil export terminal, and its role in the country’s energy infrastructure is strategically significant.

Lavan Island and Sirri Island are additional centers of Iran’s offshore oil industry. Hengam Island is known for its populations of dolphins and nesting sea turtles. Hormuz Island is distinguished by its colorful red soil and its historical significance as the site of the Portuguese fortress that controlled the strait for over a century.

Bahrain is the only island nation in the Persian Gulf. Bubiyan Island belongs to Kuwait. Modern artificial islands — including Dubai’s Palm Islands and The World Islands, and Doha’s Pearl Island — represent a newer phenomenon of large-scale coastal engineering in the Gulf.

Climate and Marine Conditions

The climate of the Persian Gulf is severe. Summer air temperatures regularly exceed 50 degrees Celsius along the coast, and humidity frequently surpasses 90 percent. Sea surface temperatures in summer routinely exceed 35 degrees Celsius, placing the Gulf among the hottest marine environments on Earth.

The only significant freshwater input is the Arvand Rud, delivering approximately 2,000 cubic meters per second. On the Iranian side, the Karun, Zohreh, Mand, and Minab rivers also contribute freshwater, though their combined volume is modest compared to the Arvand Rud. Annual evaporation is extremely high — about 1.8 meters — while rainfall is negligible, at roughly 0.08 meters per year. This imbalance drives salinity to 37-42 parts per thousand across most of the Gulf, well above the oceanic average of about 35 parts per thousand. In the shallow southern reaches, salinity can climb to 50 parts per thousand or higher.

The shamal winds blowing from Iraq and Saudi Arabia play an important role in moderating water temperatures. These winds generate evaporative heat flux exceeding 300 watts per square meter, cooling the sea floor and helping to sustain coral health — a mechanism documented by research at New York University Abu Dhabi.

The complete renewal time for water in the Gulf is estimated at two to five years. This slow flushing rate means that any pollutant entering the Gulf persists for years before being diluted or expelled through the Strait of Hormuz — a fact that dramatically increases the Gulf’s environmental vulnerability compared to open-ocean environments.

The Iranian coastline supports important biological features. Mangrove forests (known locally as hara) on Qeshm and other islands constitute the most extensive mangrove systems in the Persian Gulf. The Hara Protected Area on Qeshm provides habitat for migratory birds and nesting sea turtles. Beyond the mangroves, the Iranian coast includes mudflats, salt marshes (sabkha), and coral reef formations.

Historical Significance

The Persian Gulf has served as a corridor between civilizations for thousands of years, and its history is inseparable from the broader story of maritime trade, imperial expansion, and great-power rivalry across western Asia.

Ancient Civilizations and Maritime Trade

The earliest known Gulf civilization was Dilmun, a trading center located primarily in present-day Bahrain that served from the third millennium BCE onward as a crucial intermediary between Mesopotamia and the Indus Valley. Sumerian cuneiform tablets describe Dilmun as a sacred and prosperous land. In Sumerian mythology, the water god Enki called Dilmun a land of purity and paradise. The golden age of Dilmun lasted from roughly 2200 to 1600 BCE, during which copper from Oman, timber and gemstones from the east, and grain from Mesopotamia were exchanged through its ports. By 567 BCE, Neo-Babylonian administrative records show that Dilmun had come under the authority of the King of Babylon.

On the Iranian shore, Liyan (ancient Bushehr) was an important Elamite center. Inscribed bricks from Middle Elamite rulers, including Humban-Numena (circa 1350-1340 BCE), have been recovered there. Cross-Gulf trade networks are confirmed by soft-stone vessels from the Oman peninsula found at Liyan and Dilmun-style stamp seals unearthed at Susa. Near Borazjan, south of Bushehr, three Achaemenid monumental buildings have been excavated, including the Winter Palace of Bardak Siah, attesting to Persian imperial investment along the Gulf coast from the earliest period.

Achaemenid and Hellenistic Periods

With the establishment of the Achaemenid Empire around 550 BCE, the Gulf became an imperial naval highway. Persia (modern Iran) established naval bases in Bahrain, Oman, and along the Arvand Rud estuary. Darius the Great ordered the construction of a canal connecting the Nile to the Red Sea, intended to link Mediterranean commerce with Persian Gulf trade routes. The ports along Iran’s Gulf coast became the principal centers of the empire’s maritime trade with India and regions further east.

Following Alexander’s conquests, his admiral Nearchus sailed through the Persian Gulf around 325 BCE, traveling from the mouth of the Indus to the Euphrates delta. In his account, he repeatedly used the term Persikon Kolpon (Persian Gulf). The voyage of Nearchus produced one of the earliest detailed descriptions of the Gulf’s coastline, its winds, its tides, and its coastal communities.

During the Parthian period (circa 130 BCE to 224 CE), the Arsacid Empire extended its influence southward, establishing garrisons along the Gulf’s southern coast and maintaining Persia’s naval presence as far as Oman.

Sassanid Era and the Port of Siraf

Under the Sassanid dynasty (224-651 CE), the Persian Gulf came under direct Iranian sovereignty, and Persian Gulf ports flourished as never before. The Sassanids maintained maritime trade routes connecting Iran with India, East Africa, and China. The earliest direct commercial contacts between the Persian Gulf and China by sea date to approximately the second century CE.

The port of Siraf in Bushehr Province became the most prosperous harbor on the Gulf. At the height of its influence under the Abbasid caliphate (circa 750-1050 CE), Siraf was the premier international trading port of the Persian Gulf. Sirafi merchants imported silk and porcelain from China, spices from India and Indonesia, and ivory and gold from East Africa. The voyages of Sindbad the Sailor, a fixture of the Thousand and One Nights, are widely believed to have been inspired by the journeys of Sirafi sea captains.

David Whitehouse of the British Institute of Persian Studies, working alongside Gholam-Reza Masoumi from Iran’s Institute of Archaeology, conducted seven seasons of systematic excavation at Siraf between 1966 and 1973. These excavations uncovered a large congregational mosque — among the earliest in Iran — merchants’ mansions reflecting considerable wealth, and over 16,000 artifacts including extensive Chinese ceramics from the Tang dynasty. The city’s origins traced back to the Sassanid period. A 2012 underwater archaeology project discovered stone anchors and building materials beneath eight meters of water, confirming the port’s maritime importance and the extent of coastal erosion since its active period.

A devastating earthquake around 970 CE destroyed much of Siraf, and maritime trade shifted to Kish Island, which served as the Gulf’s principal commercial center for the following centuries.

Islamic Period and Muslim Geographers

Following the Arab conquests of the seventh century, migration of Arab tribes to the Gulf coasts increased, and Muslim merchants — both Arab and Persian — established extensive trade networks linking the Persian Gulf to India, East Africa, and China. A triangular trading system connecting India, China, and East Africa operated through the Gulf’s ports.

Medieval Muslim geographers unanimously used the name Bahr Faris (Persian Sea) or Khalij Faris (Persian Gulf). Al-Istakhri (died circa 951 CE), a Persian from near Persepolis, wrote Bahr Faris in both his text and his maps. Al-Masudi (circa 896-956 CE), often called the Herodotus of the Arabs, used both Bahr Faris and Khalij Faris in his Muruj adh-Dhahab (Meadows of Gold). Ibn Hawqal continued this convention. Yaqut al-Hamawi (1179-1229), himself of Byzantine Greek ancestry, wrote of “the sea of Faris” in his monumental geographical dictionary Mu’jam al-Buldan. Even Ibn Khaldun used Khalij Faris in his Muqaddimah. The maps of Abu Zayd al-Balkhi from the 920s CE clearly label Bahr-e-Fars.

Some of these geographers applied Bahr Faris more broadly than the modern boundaries of the Persian Gulf, sometimes extending the term to include the Gulf of Oman and portions of the Indian Ocean as far as the coasts of China. More than thirty geographical and historical texts by Muslim scholars explicitly use the name “Persian Gulf” or “Persian Sea.”

Portuguese and the Strait of Hormuz

In the sixteenth century, Portugal under the command of Afonso de Albuquerque captured the island of Hormuz in 1507 (886 Solar). Hormuz, situated at the mouth of the strait, commanded all maritime trade entering or leaving the Persian Gulf.

The Portuguese maintained control over the Strait of Hormuz for approximately 115 years. They built fortresses on Hormuz, Qeshm, and Bahrain, and collected heavy customs duties from passing vessels. In all Portuguese maps and correspondence from this period — more than fifty known documents — the name used was consistently “Sea of Persia” or its Latin and Portuguese equivalents: Mare de Persia, Mar Persiano, Persico Sinus.

In 1615, Shah Abbas I of the Safavid dynasty captured the port of Gamrun and renamed it Bandar Abbas (Port of Abbas). In 1622 (1001 Solar), Shah Abbas, with naval support from the English East India Company, expelled the Portuguese from Hormuz in a combined Anglo-Persian military operation. This event is now commemorated annually in Iran as National Persian Gulf Day (the 10th of Ordibehesht, falling on April 30).

Britain and the Making of the Modern Gulf

From the eighteenth century onward, Britain progressively extended its dominance over the Persian Gulf. The British Residency in the Persian Gulf operated from 1822 to 1971 — a span of 149 years — and effectively drew the modern political map of the region.

The General Maritime Treaty of 1820 with the Arab sheikhs of the southern coast initiated British involvement. Its stated purpose was the suppression of piracy. The Perpetual Maritime Truce of 1853 established the “Trucial Coast” — the territory that would later become the United Arab Emirates. Exclusive agreements in the 1880s and 1890s ceded the foreign affairs and defense of the sheikhdoms to Britain, while oil concession agreements between 1913 and 1937 determined which companies would exploit the Gulf’s petroleum resources.

The British Residency was headquartered in Bushehr on the Iranian coast. J.G. Lorimer compiled the Gazetteer of the Persian Gulf, Oman, and Central Arabia (1908-1915), the most comprehensive written reference on the region from the colonial era. This work remains a standard scholarly reference and is accessible through the Qatar Digital Library.

Throughout the entire 149 years of British presence, the name “Persian Gulf” was used exclusively in all treaties, maps, administrative documents, and nautical charts. The American-Lebanese writer Ameen Rihani, visiting the Gulf in 1930, wrote:

The Gulf should be renamed — it is neither Persian nor Arabian; it is British.

Ameen Rihani, 1930

On January 16, 1968, British Prime Minister Harold Wilson announced Britain’s withdrawal from “East of Suez.” The result was the formation of the United Arab Emirates (December 2, 1971) and the independence of Bahrain and Qatar as separate sovereign states.

Pearling: The Pre-Oil Economy

Before the discovery of oil, the economic backbone of the Persian Gulf was pearl diving — an industry with at least four thousand years of documented history. Pliny the Elder in the first century CE described Tylos (Bahrain) as famous for “the vast number of its pearls.”

The pearl industry reached its peak in 1912 — known in Gulf maritime culture as the “Year of Superabundance.” At that time, approximately 74,000 men on both coasts of the Gulf were engaged in pearling, representing more than 25 percent of the Arabian coast’s total population. Pearl grounds extended from Bushehr and Khark Island on the Iranian shore to Kuwait, Bahrain, Qatar, and the Trucial States on the Arabian side.

The organizational culture of pearl diving was elaborate and hierarchical:

• Nakhuda: the owner and captain of the boat
• Nahham: a singer who set the daily rhythm through ritual prayers and chants
• Ghawwas (diver): descended using only a nose clip, reaching depths of 6 to 20 meters, remaining underwater for 60 to 90 seconds per dive, and completing 30 to 40 dives daily
• Sib: the rope-holder who managed the diver’s line

The diving season ran from spring through early autumn. A tradition of firing a pistol shot marked the discovery of a large pearl, the sound carrying to shore. Women gathered at the coast, beating the sea with palm branches to coax the wind into the sails of returning boats.

The invention of cultured pearls by Kokichi Mikimoto in 1893, combined with the Great Depression of the 1930s, destroyed this millennia-old trade within a single decade. UNESCO has described the collapse as “sudden and catastrophic.” Kuwait’s pearl market officially closed in 2000. Today, “Persian Gulf Pearl” is registered as a geographical indication under the WIPO Lisbon Agreement (2018), and Bahrain’s pearling heritage — a complex of 17 buildings, three offshore oyster beds, and a 3.5-kilometer visitor pathway in Muharraq — holds UNESCO World Heritage status.

Oil Discovery and Regional Transformation

The discovery of oil fundamentally transformed the Persian Gulf. Petroleum was first found in Iran in 1908 at Masjed Soleyman, but the Gulf’s wider economy remained dependent on pearling and fishing until the 1930s. Oil was subsequently discovered in Bahrain (1932) and in Saudi Arabia and Kuwait (1938).

Oil concession agreements signed between 1913 and 1937 determined which companies would extract the Gulf’s petroleum. The 1973 oil crisis — the OPEC embargo following the Yom Kippur War — dramatically underscored the strategic importance of the Persian Gulf, revealing the depth of Western dependence on Gulf energy supplies. This crisis permanently elevated the Gulf’s profile in global geopolitics and set the stage for the military, diplomatic, and economic competition that has characterized the region ever since.

The Name “Persian Gulf”

The naming dispute over the Persian Gulf is one of the longest-running geographical-political controversies of the modern era, and understanding it requires separating historical evidence from political claims.

Historical Evidence

“Persian Gulf” is among the oldest continuously documented geographical names in the world, with over 2,500 years of recorded usage across dozens of languages and civilizations.

The earliest known royal reference appears in the inscriptions of Darius the Great (reigned 522-486 BCE), erected on five pink granite steles along the canal connecting the Nile to the Red Sea. Discovered near Suez in 1866, the Old Persian text (catalogued as DZc) reads:

I ordered the digging of this canal from a river called Nile, which flows in Egypt, to the sea which begins in Persia.

Darius the Great, Inscription DZc (5th century BCE)

The critical phrase — draya tya haca Parsa aitiy (“the sea which begins in Persia”) — is the oldest known royal inscription linking this body of water to the name of Persia (modern Iran).

Greek and Roman geographers used the name without ambiguity. Strabo employed “Persian Gulf” or “Persian Sea” in at least six separate passages across Books 2, 11, 15, 16, and 17 of his Geography. In passage 16.3.1, he wrote: “The Persian Gulf is also called the Persian Sea.” Pliny the Elder described the Gulf’s dimensions in his Natural History: “The Persian Gulf, at the entrance, is only five miles wide.” Ptolemy consistently used Sinus Persicus in his Geographia, and his Sixth Map of Asia bears the subtitle “Arabiam Felicem, Carmaniam ac Sinum Persicum.”

A critical point of historical linguistics: in ancient Greco-Roman usage, the term “Arabian Gulf” (Sinus Arabicus) referred to the Red Sea, not the Persian Gulf. The maps of Hecataeus, Herodotus, and Ptolemy all maintain this distinction clearly. The UNGEGN Working Paper presented to the United Nations noted this explicitly, pointing out that Arab states need not alter a historical name to have a gulf of their own, since a body of water already bore their name — what is now called the Red Sea.

The strongest body of historical evidence comes from medieval Muslim geographers — scholars who, under the logic of modern Arab nationalism, might have been expected to use a different name, but uniformly did not. Al-Istakhri, Al-Masudi, Ibn Hawqal, Yaqut al-Hamawi, and Ibn Khaldun all wrote Bahr Faris or Khalij Faris in their major works. More than thirty Arabic and Muslim geographical texts use this name explicitly. Even a 1952 Saudi ARAMCO map bears the Arabic form al-Khalij al-Farisi (Persian Gulf).

The European cartographic tradition was equally consistent. From Mercator’s 1541 globe (Sinus Persicus) to Bellin’s 1763 Carte Du Golphe Persique, the name remained constant. Of more than 6,000 historical maps dated up to 1890, only a handful used any name other than “Persian Gulf.”

Origin and Development of the Dispute

The alternative designation “Arabian Gulf” for this body of water has no documented history before the mid-twentieth century. The earliest significant Western use traces to Roderic Owen, a British diplomat, in his 1957 book The Golden Bubble. Sir Charles Belgrave — British adviser to Bahrain’s ruler — used the term in the journal Soat al-Bahrain in 1955 and is often identified as the earliest Western promoter of the alternative name.

The broader renaming movement gained momentum during the 1960s under the influence of Gamal Abdel Nasser’s pan-Arab nationalism. The catalyzing event was specific: on July 23, 1960, the Shah of Iran revealed official Iranian ties with Israel at a press conference in Tehran, provoking Nasser’s fury. The Arab League subsequently circulated a directive to member states requesting the adoption of “Arabian Gulf.”

A telling detail: Nasser himself, in an official letter to a Bahraini official dated August 30, 1951, used the Arabic form al-Khalij al-Farisi (Persian Gulf). Even the principal advocate of the renaming campaign had used the historical name before the political rupture with Iran.

The Gulf Cooperation Council incorporates “Arabian Gulf” in its organizational identity — its formal name is “Cooperation Council for the Arab States of the Gulf” — but no standalone formal resolution dedicated exclusively to the naming question has been located. The name change was a gradual political process, not a single institutional decision with a documented session number and text.

Notable incidents in the dispute include the 2004 controversy when National Geographic printed “Arabian Gulf” in parentheses beneath “Persian Gulf” on its maps, prompting Iran to ban the magazine. National Geographic reversed the decision by December of that year. In 2010, the Islamic Solidarity Games in Iran were canceled over the naming dispute on medals and insignia. In 2012, Iran threatened legal action against Google for omitting the name “Persian Gulf” from Google Maps.

International Organizations’ Positions

United Nations: The UN Secretariat has issued at least eight directives mandating the use of “Persian Gulf.” The most significant is the editorial directive of August 18, 1994 (ST/CS/SER.A/29/Add.2), which stipulated:

The full name Persian Gulf should be used in every case instead of the shorter term Gulf.

UN Secretariat Editorial Directive, August 18, 1994

The 1999 follow-up directive confirmed: “The term Persian Gulf is used in Secretariat documents and publications as the standard geographical designation.” The UN Division for Ocean Affairs and the Law of the Sea uses “Persian Gulf” on its official website.

International Hydrographic Organization: The third edition of Limits of Oceans and Seas (S-23), published in 1953, lists this body of water in Section 41 as “Gulf of Iran (Persian Gulf).” A proposed fourth edition circulated in 2002 retained the Persian Gulf name but was withdrawn over a separate dispute involving the Sea of Japan/East Sea. In 2020, IHO member states adopted a digital workaround (the S-130 standard) using numeric identifiers rather than names. The 1953 edition remains the governing legal baseline.

U.S. Board on Geographic Names: The BGN retains “Persian Gulf” as its official federal standard. In 2020, the Board issued a formal statement reaffirming this position. However, the U.S. Fifth Fleet stationed in Bahrain has used “Arabian Gulf” in operational communications since approximately 1991 — a practice that public affairs officers have described as a “friendly, solidarity gesture” with the host country.

Associated Press Stylebook: Describes “Persian Gulf” as “the long-standing name and the best choice” for the body of water.

Perspectives

Iranian perspective: Iranians across the political spectrum — from government officials to diaspora activists, from monarchists to republican opposition — regard “Persian Gulf” as a historical, legal, and cultural fact. This is one of the rare issues on which virtually all Iranians agree regardless of political affiliation. Iran cites eight UN Secretariat directives, the IHO standard, and more than 6,000 historical maps in support of the name. Iran observes the 10th of Ordibehesht (April 30) each year as National Persian Gulf Day, commemorating Shah Abbas I’s 1622 expulsion of the Portuguese from Hormuz.

Arab perspective: Six or seven Arab states border the Gulf compared to one non-Arab state. Proponents of “Arabian Gulf” argue that contemporary demographic and political realities should be reflected in nomenclature, and that the Gulf constitutes an Arab political and cultural space. The name “Arabian Gulf” has become normalized in Arab sports, education, and media. However, several prominent Arab historians and intellectuals have acknowledged that the historical name was “Persian Gulf” and that the change began in the Nasser era. Saudi historian Abdel Khaleq al-Janabi confirmed this, as have other Arab scholars including Abdelhadi Tazi, Ahmad al-Saraf, and Yusuf al-Qaradawi.

International legal perspective: Ali Omidi’s 2024 analysis in the Chinese Journal of Comparative Law (Oxford Academic) applied four criteria from international law — historical reasoning, critical date theory, judicial precedent, and treaty obligations — and concluded that the International Court of Justice’s principle of prior in tempore potior in jure (“first in time, stronger in right”) firmly supports “Persian Gulf.” The critical date, Omidi argues, is 1957-1960, when Arab states began abandoning a name they had themselves used for centuries. Masoud Zamani’s 2025 analysis on EJIL Talk reinforced this conclusion by applying the ICJ’s 2011 Macedonia v. Greece precedent.

Island Sovereignty

The dispute over three islands in the Persian Gulf is one of the most complex territorial controversies in the Middle East, with historical, legal, and geopolitical dimensions.

Abu Musa and the Greater and Lesser Tunbs

Three islands — Abu Musa, Greater Tunb, and Lesser Tunb — sit along the approaches to the Strait of Hormuz and occupy positions of considerable strategic importance. Iran has exercised full administrative and military control over all three islands since 1971 (1350 Solar). The United Arab Emirates claims sovereignty over all three.

Abu Musa is the largest of the three, with a small resident population and a known deposit of red iron oxide. The two Tunb islands are smaller and less populated. Their strategic significance derives from their location near the shipping lanes of the strait, which gives whoever controls them considerable influence over maritime traffic through the Gulf’s only outlet.

Historical and Legal Context

On November 30, 1971 — one day before the formal establishment of the United Arab Emirates and following Britain’s announcement of withdrawal from east of Suez — Iran deployed military forces to all three islands. Britain, already in the process of departing, did not intervene.

For Abu Musa, Iran and the Emirate of Sharjah signed a memorandum of understanding. Under its terms, Iran stationed military forces on the island while the Sharjah flag remained over civilian areas and Sharjah retained civil administrative authority. Iran later modified aspects of this arrangement. For Greater Tunb and Lesser Tunb, no such understanding was reached; Iran’s takeover of these islands was opposed by Ras al-Khaimah.

The historical evidence is ambiguous and contested on both sides. Iran points to Portuguese-era maps, older administrative documents, and continuous Iranian presence. A significant moment occurred in 1904, when Iran lodged a formal protest against the raising of the British flag over the islands. The UAE cites British colonial records and the authority of the Qasimi sheikhdom (present-day Ras al-Khaimah) over the islands during the colonial period.

A widely circulated but unverified theory holds that Iran’s withdrawal of its claim to sovereignty over Bahrain — a process managed by Britain through a UN-supervised referendum — was part of an implicit understanding in which Britain would acquiesce to Iranian control over the three islands. No written document confirming such a deal has ever been produced.

Perspectives

Iranian perspective: The three islands are an inseparable part of Iranian territory. Iran’s sovereignty over them has a history stretching back centuries, supported by administrative and military documentation. The Abu Musa memorandum of understanding, in Iran’s reading, confirms rather than qualifies Iranian sovereignty.

UAE and GCC perspective: The islands were illegally occupied by Iran in 1971. The UAE has called for direct bilateral negotiations or referral to the International Court of Justice. The GCC has supported the UAE’s position, and a joint GCC-EU statement described Iran’s presence on the islands as “occupation.”

Legal assessment: The historical evidence presented by both sides is incomplete and selective. Iran holds effective control — both military and administrative — over the islands. The UAE maintains a legal claim backed by significant international diplomatic support. Resolution of the dispute without a major geopolitical shift appears unlikely.

Marine Ecosystem

Despite its extreme environmental conditions, the Persian Gulf supports species found nowhere else on Earth — a characteristic that makes it an irreplaceable natural laboratory for studying climate adaptation.

Heat-Tolerant Corals

Corals of the Persian Gulf survive the hottest coral waters on the planet. Summer sea surface temperatures routinely exceed 35-36 degrees Celsius, representing the highest known thermal limit for coral survival globally. Part of this remarkable resilience is attributable to Symbiodinium thermophilum, a heat-tolerant symbiotic alga identified in 2015 by Hume and colleagues in Scientific Reports. Research by Howells and colleagues (2016, Global Change Biology) demonstrated that genetic adaptation also plays a significant role. Studies by John Burt at New York University Abu Dhabi showed that shamal wind events cool sea-bottom temperatures through evaporative heat flux exceeding 300 watts per square meter, helping to moderate bleaching severity.

However, this adaptation appears to be approaching its ceiling. Repeated coral bleaching events have been documented across recent decades, and Acropora (staghorn coral) has declined sharply in many areas. Iran harbors some of the Gulf’s richest coral diversity, particularly around Larak Island, but that resilience does not remove the broader ecological risk.

The Persian Gulf contains approximately 2,000 square kilometers of coral reef — less than one percent of the global total — but the scientific value of these heat-tolerant corals for understanding climate adaptation is without parallel.

Biodiversity

The Persian Gulf supports one of the most important dugong habitats outside Australia. These populations remain under pressure from poaching, bycatch in fishing nets, and the degradation of seagrass beds caused by dredging and hypersaline discharge.

Whale sharks congregate around Qatar’s Al Shaheen oil field area, where cold upwelling creates conditions favorable for fish egg incubation. Five sea turtle species nest on Iranian islands including Hormuz, Larak, Qeshm, and Hengam, with hawksbill turtles classified as critically endangered.

Overall, the Gulf supports more than 2,000 marine species, including over 700 fish species, 32 shark species, and 12 marine mammal species, among them Indo-Pacific humpback dolphins. The Gulf’s seagrass beds function as significant carbon sinks, playing an important role in carbon dioxide absorption. Traditional small-scale fishing still accounts for a major share of the coastal economy across many parts of the Gulf.

Pollution and Environmental Threats

Oil pollution represents one of the most severe environmental threats to the Persian Gulf. During the 1991 Gulf War, a vast quantity of crude oil was deliberately released into the sea in what is widely described as the largest intentional oil spill in history. The spill contaminated long stretches of coastline, killed large numbers of seabirds, and left ecological damage that persisted for years.

A 1993 UNESCO assessment reporting “little long-term damage” was premature and widely disputed. Dr. Jacqueline Michel’s 2010 study found that oil remained present twelve years after the spill, having penetrated 40 to 50 centimeters into coastal sediments — trapped beneath layers of sand and microbial films. Joydas and colleagues (2017) found that enclosed bays still contained “alarming levels” of hydrocarbons threatening marine life.

Desalination brine poses a growing threat. The Gulf hosts one of the world’s densest concentrations of desalination plants, and the resulting hot, hypersaline discharge places continuous stress on the marine ecosystem. At the same time, many Gulf states depend heavily on desalination for drinking water, making marine degradation and infrastructure disruption doubly consequential.

Regional Cooperation and Conservation

The Regional Organisation for the Protection of the Marine Environment (ROPME), established in 1979 under the Kuwait Regional Convention, includes all eight littoral states as members. ROPME coined the neutral term “ROPME Sea Area” as a diplomatic workaround to avoid the naming dispute.

ROPME coordinates 173 marine protected areas covering 7.8 percent of the ROPME Sea Area. However, only 37 percent of these areas have formal legal designation, and management effectiveness averages just 34 percent. A critical gap remains the absence of binding regional standards for desalination brine discharge — a failure that is particularly significant given the Gulf’s role as the world’s largest concentration of desalination plants.

Climate change compounds all other pressures. Marine heatwaves are becoming more frequent, and long-range modeling points to additional warming over the course of the century. Unlike other warming seas, the Persian Gulf faces a unique constraint: no warm-adapted species can migrate into the Gulf through the Strait of Hormuz, its sole connection to the open ocean. Expanding hypoxia, harmful algal blooms, and jellyfish proliferation threaten both marine life and the desalination plants on which Gulf populations depend for freshwater.

A recent regional assessment found that a large share of assessed habitats and organisms in the Persian Gulf remain data-deficient, while many others are already in decline — a finding that underscores how much remains unknown about this ecologically distinctive body of water.

Economy and Energy

The Persian Gulf sits at the heart of the global energy market, and any disruption to its flows carries immediate consequences for the world economy.

Oil and Gas Reserves

The eight littoral states of the Persian Gulf collectively hold a major share of the world’s proven oil and natural gas reserves. The concentration of hydrocarbon wealth along one semi-enclosed body of water is without parallel anywhere else on Earth.

The most significant individual fields include:

• Safaniya (Saudi Arabia): the world’s largest offshore oil field
• South Pars/North Dome (straddling the Iran-Qatar maritime boundary): the world’s largest natural gas reserve
• Ghawar (Saudi Arabia, near the Gulf coast): the world’s largest conventional onshore oil field

Together, these three fields alone represent a substantial fraction of total global hydrocarbon reserves. The shared South Pars/North Dome field is particularly significant: it underlies an area of roughly 9,700 square kilometers on the seabed of the Persian Gulf, with Iran controlling the southern portion (South Pars) and Qatar the northern portion (North Dome).

Energy Transit and the Strait of Hormuz

The Strait of Hormuz is the world’s most important energy chokepoint. Under normal conditions, very large volumes of oil, petroleum products, and liquefied natural gas transit the strait each day. Most of this trade is bound for Asian markets, especially East and South Asia, which helps explain why tension in the strait has immediate global effects.

Only Saudi Arabia and the UAE possess pipeline infrastructure capable of bypassing the strait. Saudi Arabia’s East-West pipeline from Abqaiq to Yanbu on the Red Sea has a design capacity of five million barrels per day. The Abu Dhabi Crude Oil Pipeline (ADCOP) carries approximately 1.5 million barrels per day to the port of Fujairah on the Gulf of Oman. However, the combined capacity of bypass pipelines remains modest relative to the total volume of strait traffic, meaning that no realistic alternative exists for the bulk of Persian Gulf energy exports.

Iranian Ports and Economic Zones

Iranian ports along the Persian Gulf play a central role in the national economy:

• Bandar Abbas (Shahid Rajaee Port): Iran’s main maritime gateway on the Gulf coast
• Bushehr: the oldest active Iranian port on the Gulf, capital of Bushehr Province, and site of the Bushehr nuclear power plant
• Khark Island: the principal terminal for Iranian crude oil exports
• Asaluyeh (Pars Special Energy Economic Zone): the onshore processing center for South Pars gas and a major petrochemical hub
• Kish: a free trade zone focused on tourism and financial services
• Qeshm: a free trade zone with UNESCO Global Geopark status

In southern Iranian waters, lenj boats and other small craft still sustain coastal livelihoods. Fisheries remain an important part of the maritime economy, even as offshore oil and gas dominate national revenue.

Maritime Cultural Heritage

The maritime cultural heritage of the Persian Gulf is far richer than its modern association with oil and geopolitics would suggest — and much of this heritage is in danger of disappearing.

Lenj Boatbuilding and Traditional Seafaring

Lenj boatbuilding — the hand construction of traditional wooden sailing vessels — was inscribed on UNESCO’s List of Intangible Cultural Heritage in Need of Urgent Safeguarding in 2011. Lenj boats are built entirely without blueprints by master craftsmen known as ghallaf. A team of five to six skilled builders requires approximately two years to complete a single vessel.

Lenj boats once sailed from southern Iran to Mumbai, Basra, Zanzibar, and the coast of China, carrying trade goods across the Indian Ocean. The navigation knowledge associated with lenj seafaring included reading weather conditions from water color and wave height, and assigning a name to each wind — centuries of accumulated maritime intelligence passed orally from master to apprentice.

Today, the community of active lenj builders is small and aging. Fiberglass vessels have largely replaced wooden construction, and the economic conditions that sustained traditional boatbuilding have long since disappeared. The Gouran Maritime Park-Museum on Qeshm Island preserves 28 pictorial displays and 14 original vessels, serving as a record of a tradition that may not survive another generation in living practice.

Pearling in Culture and Literature

The pearl industry was not merely an economic activity — it sustained a rich culture with its own music, social hierarchy, and seasonal rituals. The nahham (ship singer) regulated the rhythm of the diving day through ritual chants and prayers. These songs form part of the broader tradition of Bandari music, rooted in the maritime culture of the Persian Gulf coast.

The seasonal calendar of pearling began in spring and ended in early autumn. Social roles — nakhuda (captain), ghawwas (diver), sib (rope-holder), tawwash (pearl broker) — formed a precise hierarchy. The pearl economy operated as a transnational network: Gulf pearls were primarily exported to world markets through Mumbai.

The economic scale of the pearl industry at its peak was considerable. By the late nineteenth and early twentieth centuries, Gulf pearls were a major export commodity until the Japanese cultured pearl industry devastated the trade.

The Persian Gulf in Iranian Poetry and Art

Persian literature carries echoes of the Gulf, though direct references in classical poetry are fewer than one might expect. The sea in classical verse functions more often as metaphor than as a specific geographical location.

The Shahnameh of Ferdowsi (completed circa 1010 CE) contains references to Daryaye Pars (Sea of Persia). Pre-Islamic Zoroastrian Pahlavi texts also use this term. The pearl imagery pervading the works of Hafez, Saadi, and Rumi draws indirectly from the Gulf’s pearling tradition. Hafez’s celebrated ghazal describing “a pearl which in no shell of time and space abode” resonates with the culture of a region where pearl diving had been practiced for millennia.

In modern poetry, Manuchehr Atashi (1931-2005), born in Bushehr Province on the Gulf coast, built an entire poetic voice around “the sea and the warm land of palm trees.” Atashi is regarded as the poet of the Persian Gulf and southern Iran, and his work brought the voice of the Gulf’s coastal communities into the mainstream of Persian literature. The contemporary poet Rosa Jamali wrote more directly:

And it was over! The Gulf was over!
You waved hands.

Rosa Jamali

Iranian stamps, coins, and medals have repeatedly depicted the Persian Gulf. The traditional wind-catcher architecture (badgir) — a natural ventilation system — has its roots directly in the hot, humid climate of the Gulf coast and remains visible in Bandar Abbas, Bushehr, and across the islands. Bandari cuisine, with its emphasis on fish, shrimp, and Indian Ocean spices, reflects centuries of cultural exchange through the Persian Gulf. Qalieh mahi (fish stew) and saboor (a prized local fish) are among the signature dishes of the Iranian Gulf coast.

Geopolitics and Future Outlook

The Persian Gulf sits at the intersection of energy, geopolitics, and cultural heritage, and its future carries weight comparable to its past.

Great Power Competition

The Persian Gulf has been an arena for great-power competition from the Achaemenids and Sassanids through the Portuguese and the British to the present day.

During the Iran-Iraq War (1980-1988), the “Tanker War” phase (1984-1988) drew both belligerents into attacking commercial shipping and oil tankers in the Gulf. American and Western naval vessels intervened to escort commercial shipping. Operation Praying Mantis (April 1988) was the largest American naval engagement since World War II.

The U.S. Fifth Fleet has been stationed in Bahrain since 1991. American military presence in the Gulf has faced persistent Iranian opposition, and recurring tanker, naval, and air incidents have characterized the relationship.

China’s dependence on Gulf energy has grown steadily, while the Gulf’s export patterns are increasingly oriented toward Asian markets. Yet American military dominance in the Gulf remains unmatched, and the region continues to sit at the intersection of U.S., Chinese, Russian, and regional strategic calculations.

The Gulf has also been the scene of sustained rivalry between Iran and Saudi Arabia — a competition that in recent decades has acquired sectarian, geopolitical, and economic dimensions. The normalization of relations brokered by China in March 2023 demonstrated that diplomacy retains space in the region, though structural tensions persist.

Iran and the Persian Gulf in the Twenty-First Century

Iran has sought to deepen its ties with eastern powers and reduce dependence on Western channels, while Russia and China have expanded their diplomatic and economic room to operate in the Gulf. Even so, sanctions risk, regional mistrust, and domestic political complexity continue to limit how far those relationships can develop in practice.

The global energy transition away from fossil fuels will, over the long term, reduce the strategic importance of the Persian Gulf’s oil and gas reserves. This process, however, is measured in decades rather than years. Gulf states are already pursuing diversification, even as hydrocarbons continue to anchor state revenue, infrastructure, and regional influence.

The Persian Gulf is not merely an energy corridor. It is a cultural landscape with four thousand years of maritime civilization, an ecological system harboring species found nowhere else on Earth, and a body of water bearing one of the oldest documented geographical names in human history. Protecting this heritage — natural, cultural, and linguistic — is a shared responsibility of all its littoral nations. The future of the Persian Gulf will be determined by the balance between economic exploitation and environmental stewardship, between national ambition and regional cooperation, and between the weight of history and the pressures of a rapidly changing world.