The Strait of Gibraltar

What it is

The Strait of Gibraltar is a 58-kilometer-long channel connecting the Atlantic Ocean to the Mediterranean Sea, separating Spain's southern coast from Morocco's Tangier peninsula. At its narrowest, the gap measures 14.2 kilometers; water depth ranges from 300 to 900 meters. The strait has no viable bypass: every commercial vessel entering or leaving the Mediterranean from the west must transit here.

The IMO adopted Resolution MSC.300(87) in May 2010, formalizing a Traffic Separation Scheme (TSS) that divides the channel into inbound and outbound lanes. UNCLOS Part III (Articles 37-44) guarantees all vessels the right of transit passage through internationally navigated straits; Spain and Morocco, as bordering states, may not suspend it.

The Gibraltar Port Authority, established in 2005, manages navigational safety, search and rescue, and port operations on the north shore. Gibraltar has become the Mediterranean's largest bunkering port, recording at least 240 million gross tonnes of vessel calls per year.

History

Spain captured Gibraltar from the Moors in 1462. British and Dutch forces took it from Spain in 1704 during the War of the Spanish Succession, and Spain formally ceded sovereignty under the 1713 Treaty of Utrecht. Gibraltar's roughly 30,000 residents voted 98.5% to retain British sovereignty in a 2002 referendum and 96% to remain in the EU in the 2016 UK referendum, but left the EU alongside the UK in January 2020. Spain has disputed British sovereignty over the territory and its territorial waters almost continuously since 1713; Madrid does not recognize British Gibraltar Territorial Waters and has contested Spanish fishing vessels' access to those waters repeatedly since the late 1990s.

Current state

Gibraltar was excluded from the UK-EU Trade and Cooperation Agreement signed in December 2020. A political agreement reached on June 11, 2025, between the UK, Gibraltar, Spain, and the EU created a fluid border removing passport checks on people crossing between Gibraltar and Spain, introduced joint Gibraltar-Spain controls at the territory's airport, and contained an explicit clause stating the accord does not affect British sovereignty. British Gibraltar Territorial Waters remain under exclusive UK control. The formal treaty still required ratification by the UK and Gibraltar parliaments as of mid-2026; roughly 15,000 workers cross the Gibraltar-Spain border daily.

Commercial traffic through the strait runs to more than 300 vessels per day, around 110,000 per year, one crossing every four to five minutes. Approximately 3.3 million barrels per day of oil and petroleum products pass through, supplying around 20% of European refining capacity's crude. Saudi Arabia, Iraq, and the UAE together account for roughly 60% of those oil flows; Algeria and Libya contribute around 25% more.

Relationships

The broader chokepoint network depends on the strait as the Mediterranean's western threshold. Cargo rerouted from the Suez Canal during the 2023-25 Houthi disruption moved via the Cape of Good Hope and entered the Mediterranean through Gibraltar, sharply increasing transit density. Morocco's Tanger Med port complex, on the African shore roughly 14 kilometers across the water, has a capacity exceeding 9 million TEU and is one of Europe's largest container transshipment hubs. The Morocco-Algeria diplomatic rupture, which closed the two countries' overland border in 2021, concentrated trans-Saharan migration pressure onto the sea crossing, making the strait the primary maritime route for irregular arrivals into Spain's Ceuta enclave and the Andalusian coast.

What to watch

• Ratification of the June 2025 UK-EU-Gibraltar treaty: both the UK and Gibraltar parliaments must approve, Spain's Congress must ratify, and any Spanish election could complicate the timeline stretching into 2026-27.
• Irregular migration pressure: the strait is the shortest sea crossing from Africa into Europe and the main route for arrivals from Morocco and West Africa; Spain recorded tens of thousands of irregular sea arrivals annually in recent years.
• Morocco's Tanger Med Phase 3 expansion, targeting 15 million TEU by 2030, which would deepen Morocco's position as a rival bunkering and transshipment hub to Gibraltar.
• A proposed Spain-Morocco rail and road fixed link under the strait, studied since the 1980s, which would transform the crossing's role in Europe-Africa land connectivity.