Strait of Hormuz

The Strait of Hormuz connects the Persian Gulf to the Gulf of Oman. Iran sits on its northern shore, while the southern coast is formed by Oman’s Musandam Peninsula, with a small part of that peninsula’s southwest belonging to the United Arab Emirates. The strait stretches roughly 104 miles, and its width ranges from about 60 miles down to 24 miles.

This waterway is the only sea route out of the Persian Gulf to the open ocean, making it one of the world’s most strategically vital choke points. Between 2023 and 2025, 20% of the global supply of liquefied natural gas and 25% of all seaborne oil passed through it each year. It serves as a major corridor for petroleum products heading to Europe and Asia, and it is essential for Europe’s energy security. For several Gulf nations—including the UAE, Qatar, Bahrain, Kuwait, and Iraq—it is the sole maritime outlet, and any disruption can lead to severe shortages.

Before the 2026 Iran War, the strait had never been closed for a long period during Middle Eastern conflicts, unlike the Straits of Tiran or Bab-el-Mandeb. Iran did occasionally threaten to shut it down and made preparations to lay mines. During the war, Iranian blockades did close the strait, sparking the 2026 Strait of Hormuz crisis.

The name “Hormuz” has unclear origins. One theory traces it to the local Persian phrase *Hur-Mogh*, meaning “Place of Dates.” Another links it to the Middle Persian pronunciation of the Zoroastrian god Ahura Mazda. Some sources favor the first explanation; others lean toward the second. A third theory claims the strait was named after Ifra Hormizd, mother of King Shapur II of Persia, who reigned from 309 to 379 AD. Yet another suggests it comes from the Greek word *hormos*, meaning “cove” or “bay.”

The 1st-century mariner’s guide the *Periplus of the Erythraean Sea* described the entrance to the Persian Gulf but did not name it. Later, from the 10th to the 17th centuries, the Kingdom of Ormus was located in this area. Starting in the 15th century, the strait’s strategic importance grew as foreign powers arrived. Portugal maintained a presence from the 16th to the 18th centuries, and its control sparked disputes with other emerging powers, such as England, which entered the region in the 17th century.

To prevent collisions, ships follow a traffic separation scheme (TSS): inbound vessels use one lane, outbound another, each lane 2 nautical miles wide, with a similar 2-nautical-mile median between them. Commercial ships from countries that are party to UNCLOS must follow the TSS during transit passage. The TSS lies within Omani territorial waters, but very large ships must use Iranian waters to the southeast because the waters closer to the UAE coast are too shallow.

Vessels traversing the full length of the strait pass through the territorial waters of both Iran and Oman. Although Iran has not ratified UNCLOS, most countries—including the United States, which also has not ratified it—claim the right of passage as codified in the convention. In 1959, Iran changed the legal status by expanding its territorial sea to 12 nautical miles and declaring it would only recognize innocent passage through the newly expanded area. Oman followed suit in 1972, expanding its territorial sea to 12 nautical miles by decree. By that year, the strait was completely “closed” by the combined territorial waters of Iran and Oman at its narrowest point, between Oman’s Great Quoin Island and Iran’s Larak Island. In 1971, Iran took control of the Greater and Lesser Tunbs islands, west of Hormuz, against Arab wishes, extending its control over the navigation channels.

During the 1970s, neither Iran nor Oman tried to block warships, but in the 1980s both countries made claims that differed from customary law. When Oman ratified UNCLOS in 1989, it submitted declarations confirming its 1981 royal decree that only innocent passage is allowed through its territorial sea, and that foreign warships need prior permission to pass. Upon signing the convention in 1982, Iran declared that only states party to UNCLOS could benefit from its contractual rights, including the right of transit passage through international straits. In 1993, Iran enacted a maritime law that conflicts with UNCLOS, requiring warships, submarines, and nuclear-powered vessels to obtain permission before innocent passage through its territorial waters. The United States does not recognize any of these claims by Oman or Iran and has contested each one.

Between 2023 and 2025, the strait carried 20% of the world’s liquefied natural gas and 25% of seaborne oil, underscoring its importance for trade. According to the U.S. Energy Information Administration, in 2011 an average of 14 tankers per day left the Persian Gulf through the strait, carrying 17 million barrels of crude oil. More than 85% of those crude oil exports went to Asian markets, primarily Japan, India, South Korea, and China.