Aden Protectorate, former British protectorate on the southern coast of the Arabian Peninsula. At its largest, the Aden Protectorate consisted of 20 Arab tribal states. It was divided for administrative purposes into two regions commonly referred to as the Eastern and Western Aden protectorates. The protectorate dissolved in 1967 when the British withdrew from the region. The corresponding land is now part of the Republic of Yemen.

Archaeological remains and biblical references indicate human activity in the area of the Aden Protectorate dating from about 2000 bc. Written records say that forces under the leadership of the Roman prefect of Egypt, Aelius Gallus, invaded the country in 24 bc. His legion penetrated well into the territory but failed to reach the south coast of Arabia and was forced to withdraw north to Egypt.

Much of the area’s history centers on the relations of the Arab states of the region with the British and the neighboring kingdom of Yemen. Throughout the Islamic era (which began in the 7th century) the Zaydi imams, or rulers, of Yemen periodically attacked the western section of southern Arabia, but invariably the Yemenis were forced to withdraw. After the British occupied Aden in 1839, individual Arab states entered into treaties with Britain to ensure protection from Yemeni annexation. The last of these treaties was signed in 1914.

In 1902 an Anglo-Turkish commission demarcated the boundaries between the Aden Protectorate and Yemen. Boundaries left undefined were eventually delineated and described by another Anglo-Turkish boundary convention in 1914. In 1934 the ruler of Yemen, Imam Yahya, who had long claimed that the protectorate and even the state of Aden formed part of his dominion—a claim always strenuously resisted by the states themselves and the British government—entered into a treaty with Britain. The terms of this treaty were in general agreement with the terms set out by the convention of 1914.

In 1963 the state of Aden became a member of the Federation of South Arabia (originally the Federation of Arab Emirates of the South). This federation was formed in 1959 by a treaty between Britain and several protectorate states. By 1965 the federation had a total of 17 member states.

Opposition to the federation was considerable. Revolutionary groups launched a campaign of terrorism aimed at destroying the federation and forcing the withdrawal of the British. By the fall of 1967, the National Liberation Front, which emerged as the leading revolutionary group, gained power throughout the Protectorate of South Arabia and forced the collapse of the federation. By December 1967 the British had withdrawn from the region, and the Aden Protectorate and Aden became independent Southern Yemen. This region then merged with North Yemen in 1990 to form the Republic of Yemen.