The Strait of Hormuz is the channel between Iran to the north and the Musandam Peninsula, mostly Omani with a southwestern part held by the United Arab Emirates, to the south that links the Persian Gulf to the Gulf of Oman and the open Indian Ocean. It is about 167 km (104 mi) long and narrows to about 39 km (24 mi), and it is the only sea passage out of the Gulf: in 2023–2025 roughly a quarter of the world's seaborne oil trade and a fifth of its liquefied natural gas passed through it each year. Behind the tanker lanes lies a less familiar strait of mangroves, salt-dome islands, fjord-like inlets and seabird colonies, home to hawksbill turtles, Socotra cormorants, dolphins and Arabian tahr, and those habitats are the subject of this guide.
Each section below starts from a named place on the strait and the species that define it, with the figures that surveys and protected-area records give for them.
The Hara Mangroves of Qeshm and the Khuran Strait
The largest mangrove ecosystem on the Persian Gulf coast grows in the channel between Qeshm Island and the Iranian mainland, known as the Khuran or Clarence Strait. The forest is dominated by a single species, the grey mangrove Avicennia marina, called "hara" in Persian, a tree of three to eight metres whose leaves are nutritious enough that local herders cut them for livestock feed. Together, the stands on Qeshm and the opposite shore cover an area of roughly 20 km by 20 km, laced with tidal channels and mud islets.
Iran created the Hara Protected Area in 1972, and the forest is now a biosphere reserve where use is limited to fishing, mainly for shrimp, boat tours and some cutting for fodder. The Khuran Strait has also been a protected Ramsar wetland since 1975, a fitting status in a country that hosted the convention itself: the Ramsar treaty on wetlands was adopted at the Iranian Caspian resort of Ramsar on 2 February 1971, the date now marked as World Wetlands Day. In winter it holds Dalmatian pelicans and greater flamingos; green turtles feed in its channels; great egrets and other herons breed here; and sea snakes hunt, breed and shelter among the roots. The mangroves are busiest in autumn and winter, when migratory birds arrive from the north.
Hawksbill Turtles at Shibderaz on Qeshm Island
Qeshm itself is the largest island in the Persian Gulf, 135 km long and about 1,491 km² in area, almost twice the size of Bahrain. Its coast holds one of the strait's most important nesting sites: the beach at Shibderaz village, a hatching area for hawksbill turtles. Hawksbills are classed as critically endangered, mainly because of fishing, and range widely along southern Asian coasts, including the Persian Gulf; the nesting beach at Shibderaz is listed among Qeshm's main attractions alongside its salt caves.
The island's dry interior is protected too. Qeshm Island is a UNESCO Global Geopark, and its key site is the Namakdan Salt Cave, about 6.6 km long and one of the longest known salt caves in the world.
Saunders's Terns on Red Hormuz Island
East of Qeshm, about 8 km off the Iranian coast near Bandar Abbas, Hormuz Island covers just 42 km². It is a salt diapir: ancient salt deposits, around 600 million years old, that have pushed up through the overlying rock like slowly flowing ice and have stood above the sea for roughly 50,000 years. Iron-rich ochre stains its beaches and cliffs red, and Iran's Department of Environment has moved to protect the ochre after years of overuse by visitors.
BirdLife International lists Hormuz as an Important Bird Area for three species: Saunders's tern, a small tern of the Indian Ocean coasts; the great thick-knee, a large, big-eyed shorebird; and the sooty gull. The island also has a small mangrove stand that survives regular submersion by seawater. Nearby Hengam Island, about 2 km south of Qeshm, is low and largely limestone, rising only to about 106 m at Nakas Mountain, and the narrowest part of the strait lies a little further east, between Iran's Larak Island and Oman's Great Quoin Island, where the territorial waters of the two countries meet.
Socotra Cormorants on the Musandam Islets
Across the strait, the rocky islets scattered around the tip of the Musandam Peninsula form a separate Important Bird Area, chosen for their seabirds: the red-billed tropicbird, the Persian shearwater, the bridled tern and the Socotra cormorant. The cormorant is endemic to the Persian Gulf and the southeast coast of Arabia, and it is declining because of coastal development, disturbance and pollution near its colonies. In 2000 its world population was estimated at about 110,000 breeding pairs, and around 12 colonies in the northern part of its range are known to have disappeared since the 1960s. The largest remaining colony, about 30,000 pairs on Bahrain's Hawar Islands, is the only protected nesting colony inside the Gulf, and since 2000 the species has been listed as Vulnerable on the IUCN Red List.
Dolphins in the Khors of Khasab
Musandam's coast is cut by steep, flooded valleys, the khors, which have earned it the nickname "Norway of Arabia". Dhows from Khasab, the region's main town, take visitors into them to watch the dolphins that are common in Musandam's waters. Research has identified important populations of the Indian Ocean humpback dolphin along the coasts of the Arabian Peninsula, especially in Oman and the United Arab Emirates.
The innermost inlet of Khasab Bay, Khor ash Sham, also holds a reminder of the strait's role as a corridor. On Telegraph Island, a rock about 160 m long, the British built a repeater station in 1864 for the Persian Gulf submarine cable, part of the telegraph link from London to Karachi. Postings there were so hot and isolated that, according to a story repeated by travel writers, the phrase "going round the bend" comes from the voyage "round the bend" of the Strait of Hormuz back to India.
Arabian Tahr and Caracal Below Jebel Harim
The Musandam Peninsula, about 1,800 km² with 49,062 people at Oman's 2020 census, is the northern end of the Hajar Mountains, called Ruus al Jibal, the "capes of the mountains". Its highest summit, Jebel Harim, reaches 2,087 m. These mountains shelter the Arabian tahr, the smallest of the tahrs, which lives on steep slopes of the Hajar range in Oman and the UAE at up to about 1,800 m, as well as the caracal and the Ruus al Jibal fan-footed gecko. Whether the Arabian leopard still survives here is unknown.
The peaks form an Important Bird Area of their own, for species such as the pallid scops owl, the plain leaf warbler, the pale rockfinch and four kinds of wheatear: hooded, variable, Hume's and red-tailed. Settlements are few: the village of Kumzar, on the strait's shore, is reachable only by boat, and its people speak their own language, Kumzari, a southwestern Iranian language with similarities to Persian, Luri, Achomi and Balochi, spoken by only 4,000 to 5,000 people and the only Iranian language spoken exclusively on the Arabian Peninsula.
Humpback Whales to the East, Dugongs to the West
Two of the region's most remarkable marine mammals live at either end of the strait. To the east, in the Arabian Sea around Oman, lives the world's only non-migratory population of humpback whales. It has been isolated for about 70,000 years, may form a separate subspecies, and numbers only around 80 animals, making it endangered. To the west, the Persian Gulf holds the second-largest dugong population in the world, estimated at 5,800 to 7,300 animals, mostly along the Gulf's southern coast. A survey of the Gulf carried out in 1986 and 1999 recorded the largest group sighting, more than 600 dugongs together, west of Qatar. Every ship leaving the Gulf passes between these two populations.
Tankers in the Traffic Lanes, 2011 to 2026
All of this wildlife shares the water with one of the world's densest flows of oil tankers. To reduce collisions, ships follow a traffic separation scheme: inbound and outbound lanes, each 2 nautical miles (3.7 km) wide, divided by a median of the same width, mostly in Omani waters. According to the US Energy Information Administration, an average of 14 tankers a day carried 17 million barrels of crude oil out of the Gulf in 2011; by 2018 the flow was 21 million barrels a day, and by 2025 it was about 15 million. Pipelines can bypass only part of it: the Habshan–Fujairah line in the UAE, opened in 2012, carries up to about 2 million barrels a day to the Gulf of Oman.
In 2026 the strait became the centre of an international crisis. From 28 February, during the war involving Iran, the United States and Israel, Iran's Revolutionary Guards broadcast that passage was "not allowed"; ships were struck, mines were reported in the channel and traffic largely stopped. A provisional ceasefire in April brought announcements of reopening, but the situation changed repeatedly, with a US naval blockade and Iranian restrictions both in force at different times; in August, Iran's National Security Council still made reopening conditional on, among other things, the lifting of that blockade. Any spill or wreck in so narrow a channel would reach the same mangroves, nesting beaches and bird islands described above.
For the wider sea these habitats open onto, read our guide to the Persian Gulf; to compare the Hara forest with mangroves elsewhere, see our global guide to mangrove forests; and to see how Hormuz ranks among other narrow sea passages, read about the world's shipping chokepoints.