The Strait of Hormuz is a strategic route for maritime oil that Iran has long used as a geopolitical bargaining chip, and Tehran has repeatedly threatened to close it in times of crisis.
In late January, a senior naval commander of Iran's Revolutionary Guard again threatened to shut it down in the event of an attack, while US President Donald Trump warned of military action if the Islamic republic failed to reach an agreement to curb its nuclear program.
Despite its frequent blockade warnings, Tehran has never acted on it, although it briefly closed part of the strait for “security” reasons during recent military exercises.
Here are the key points you need to know about the waterway.
Gateway to the Gulf
The Strait of Hormuz links the Gulf with the Indian Ocean and is located between Iran and the Musandam enclave in Oman, located at the tip of a peninsula.
Its narrowness, about 50 kilometers (30 miles), and shallow waters, no more than 60 meters (200 feet) deep, make it vulnerable to military sealing.
The strait is dotted with deserted or sparsely inhabited islands, which are of strategic importance, particularly the Iranian islands of Hormuz, Qeshm and Larak.
Also among them are the disputed islands of Greater Tunb, Lesser Tunb and Abu Mussa, which lie between the United Arab Emirates and Iran and offer an advantageous position over the Gulf, and have been under Iranian control since 1971.
Critical oil transit point
The strait is a vital corridor connecting the oil-rich Gulf with markets in Asia, Europe, North America and elsewhere.
According to the United States Energy Information Administration (EIA), the Strait of Hormuz is “one of the most important oil bottlenecks in the world.”
About a fifth of global consumption of oil and oil products flows through the strait, averaging 20 million barrels per day in 2024, according to the EIA.
About a fifth of global liquefied natural gas trade will also transit the Strait of Hormuz in 2024, mainly from Qatar, it said.
Saudi Arabia and the United Arab Emirates have infrastructure to bypass the strait, which could mitigate disruption, but their transit capacity remains very limited: around 2.6 million barrels per day.
“Large volumes of oil flow through the strait and there are very few alternative options to remove oil from the strait if it closes,” the EIA warned.
According to the EIA, more than 80% of the oil and gas that passes through the strait is destined for Asian markets.
China, a key backer of Tehran, buys more than 90% of Iran's oil exports, according to analysis firm Kpler.
Military presence
Iran's Revolutionary Guard, the ideological arm of the Islamic republic's military, controls naval operations in the Gulf and Strait of Hormuz.
Tehran has repeatedly criticized the presence of foreign powers in the region, home to the US Fifth Fleet in Bahrain and the largest US base in the Middle East in Qatar.
In 2023, Western naval forces operating in the Gulf warned ships sailing in the strait not to approach Iranian waters to avoid the risk of seizure.
There have been a series of such incidents since 2018, when US President Donald Trump withdrew from a landmark nuclear deal with Iran and reimposed crippling sanctions on the Islamic republic, triggering tensions.
Oil transit was disrupted in 1984 during the Iran-Iraq war, when both sides attacked each other's shipping, damaging or destroying more than 500 vessels in the so-called “Tanker War.”
And after Tehran placed mines in the strait, the frigate USS Samuel B. Roberts struck one in April 1988 and nearly sank.
In July of that year, an Iran Air Airbus A300 flying on the Bandar Abbas-Dubai route was shot down by two missiles fired from a US frigate, killing 290 people.
The crew of the USS Vincennes said they had mistaken the plane for an Iranian fighter jet with hostile intentions.
Maritime incidents
The Strait of Hormuz is frequently the scene of raids and attacks on ships.
The incidents multiplied after the United States withdrew in 2018 from the international agreement on Iran's nuclear program.
In 2019, unclaimed attacks on ships in the Gulf region, a downed drone and seized oil tankers raised fears of escalation between Tehran and Washington.
On July 29, 2021, an attack in the Gulf of Oman on an oil tanker operated by a company owned by an Israeli billionaire killed two people. Israel, the United States, Britain and Romania accused Tehran, which denied any involvement.
In April 2024, the Revolutionary Guard seized the Portuguese-flagged container ship MSC Aries, accusing its owner of being “linked to Israel.”
In early February, a U.S.-flagged tanker was boarded and challenged by Iranian gunboats in the strait before continuing on its way, U.S. Central Command said.
