city of Yemen. It is situated along the north coast of the Gulf of Aden (Aden, Gulf of) and lies on a peninsula enclosing the eastern side of Al-Tawāhī Harbour. The peninsula enclosing the western side of the harbour is called Little Aden.

Aden has its earliest recorded mention in the Old Testament book of Ezekiel (Ezekiel, The Book of), where it is named alongside Canneh as one of the places with which Tyre had trading connections. Canneh and Aden were the two principal termini of the spice road of western Arabia, which was in use for about a millennium until the 3rd century AD. Later, Aden continued to function as a trading centre under Yemeni, Ethiopian, or Arab control. In the 16th century the Turks established themselves as rulers there. British (British Empire) interest in Aden as a strategic base dates from Napoleon (Napoleon I)'s conquest of Egypt, a conquest that was regarded as a menace to Britain's communications with India. About 1800 the British established a garrison at Aden, and in 1802 they signed a treaty with the harbour's ruler, the sultan of Laḥij.

When steam navigation was introduced some years later, it became necessary to have a coaling station on the Red Sea route to India. Aden, which the British had captured in 1839 from the sultan, was chosen as the most suitable location and later became so heavily used as a coal-bunkering facility that it was nicknamed the “Coalhole of the East.” Certain mainland areas were purchased by the British between 1868 and 1888, and in 1937 Aden became a British crown colony. In 1953 an oil refinery was built at Little Aden, on the western side of the bay.

Aden became partially self-governing in 1962 and was incorporated in the Federation of South Arabia (comprising the former Aden Protectorate territories) in 1963. When the federation was promised independence from Britain by 1968, however, Aden became the focus of a struggle between two rival nationalist organizations, the Egyptian-supported Front for the Liberation of Occupied South Yemen (FLOSY) and the Marxist-oriented National Liberation Front (NLF), for eventual control of the country. It was as a part of the NLF-ruled People's Republic of Southern Yemen that Aden achieved its independence on Nov. 30, 1967, and became the national capital in 1968 of what was known as South Yemen, or Yemen (Aden). In 1990 North Yemen and South Yemen merged into the single country of Yemen, and Sanaa became the national capital of unified Yemen.

The contemporary city of Aden consists of three sections: Crater, the old commercial quarter; Al-Tawāhī, the business section; and Maʿallah, the native harbour area. Its economy is based almost entirely on its functions as a commercial centre for nearby states and as a refueling stop for ships; the latter activity declined considerably during the closure of the Suez Canal (1967–75). The city has some small industries, including light manufacturing, evaporation of seawater to obtain marine salt, and boatbuilding. Aden was a free port, with no customs duties, until 1970, when duties were imposed. There is an international airport at Khawr Maksar, a former Royal Air Force (RAF) base just north of Aden. The University of Aden was opened in 1970. Pop. (2004) 589,419.