Gibraltar ( jih-BRAWL-tər, Spanish: [xiβɾalˈtaɾ]) is a British Overseas Territory and city located at the southern tip of the Iberian Peninsula, on the Bay of Gibraltar, near the exit of the Mediterranean Sea into the Atlantic Ocean (Strait of Gibraltar). It has an area of 6.8 km2 (2.6 sq mi) and is bordered to the north by Spain (Campo de Gibraltar). The landscape is dominated by the Rock of Gibraltar, at the foot of which is a densely populated town area. Gibraltar is home to around 34,000 people, primarily Gibraltarians.

Gibraltar was founded as a permanent watchtower by the Almohads in 1160. It switched control between the Nasrids, Castilians and Marinids in the Late Middle Ages, acquiring larger strategic clout upon the destruction of nearby Algeciras c. 1375. It became again part of the Crown of Castile in 1462. In 1704, Anglo-Dutch forces captured Gibraltar from Spain during the War of the Spanish Succession, and it was ceded to Great Britain in perpetuity under the Treaty of Utrecht in 1713. It became an important base for the Royal Navy, particularly during the Napoleonic Wars and World War II, as it controlled the narrow entrance and exit to the Mediterranean Sea, the Strait of Gibraltar, with half the world's seaborne trade passing through it.

The sovereignty of Gibraltar is a point of contention in Anglo-Spanish relations as Spain asserts a claim to the territory. Gibraltarians overwhelmingly rejected proposals for Spanish sovereignty in a 1967 referendum, and for shared sovereignty in a 2002 referendum. Nevertheless, Gibraltar maintains close economic and cultural links with Spain, with many Gibraltarians speaking Spanish as well as a local dialect known as Llanito.

Gibraltar's economy rests on financial services, e-gaming, tourism and the port. With one of the world's lowest unemployment rates, the largest part of the labour force are resident in Spain or non-Gibraltarians, especially in the private sector. Since Brexit, Gibraltar is not a member of the European Union, but negotiations are under way to have it participate in the Schengen Agreement to facilitate border movements between Gibraltar and Spain. In June 2025, the United Kingdom, Spain and the European Union reached a preliminary political agreement to eliminate all physical border and customs inspections between Gibraltar and Spain. According to the agreement, the Policía Nacional will carry out Schengen passport checks at Gibraltar's port and airport together with Gibraltar authorities, while the land border will be completely open to both people and goods. The agreement further provides for joint Gibraltarian–Spanish collaboration on customs, indirect taxes such as tobacco and anti-money laundering efforts, including commitments to fair competition in taxation, state aid and labour. It also affirms that British sovereignty remains legally intact despite de facto Spanish administration of Gibraltar's borders. A final treaty for ratification is pending further negotiations.