ABADAN (Iran), an island situated in the delta of the Shatt-al-Arab (q.v.), 40 mi. in length, from 2 to 12 mi. in breadth, bounded on the north and east by the Karun river (q.v.) and its tributary, the Bahmishir, on the west by the Shattal-Arab, and on the south by the Persian gulf. It is known to Arabs as Jazirat-ul-Khidhr from a tomb situated on the Bahmishir dedicated to the saint of that name. Abadan is referred to by the historian Nasir Khusrau, writing in the 13th century, as the most southerly settlement of Mesopotamia, and it is not improbable that it is identical with the site of the port Charax mentioned by Herodotus. The possession of this island was long in dispute between Persia and Turkey. It was definitely allotted to Persia by the treaty of Erzerum, 1847, the Turks however retaining control of the whole of the Shatt-al-Arab while ensuring to Persia freedom of navigation.

In 1909 the Anglo-Persian Oil Company, Ltd. (q.v.), under a lease agreement with the local overlord, the sheikh of Mohammerah, established its pipeline terminus and refinery on the island between the hamlets of Braim and Bawardah, and this settlement, now known as Abadan (lat. 30 21' N., long. 48  17' E.), developed into a town of 226,103 (1956) inhabitants, organized by the Iranian government as a municipality. Deep-water jetties were built along the foreshore to facilitate the loading of tankers and the unloading of machinery. Heavy equipment includes derricks and traveling cranes, and there are several berths for goodsized vessels.

Pipelines were laid from Abadan to Masjid Suleiman (137 mi.) and from Abadan to Teheran (590 mi.). Roads include those built from Abadan to Mohammerah (9 mi.); from Abadan to Masjid Suleiman, by way of Ahwaz (78 mi. from Abadan); and from Basra (q.v.) to Sibah, opposite Abadan, on the right bank of the Shatt-al-Arab.

In 1951 the Abadan refinery, with a capacity of about 500,000 bbl. a day, was practically shut down after Iran nationalized the oil fields, and western technicians and staff members of the Anglo-Iranian Oil company, whose residence permits were revoked, were forced to leave the country. Operation by the National Iran Oil company proved unsuccessful and three years later an agreement to resume production was made between the Iranian government and a consortium of eight foreign oil companies, including the British Petroleum company (formerly the Anglo-Iranian Oil company). Even as late as 1956, however, the daily output was still only about half of what it had been before 1951, and a fire in 1958 further delayed efforts to restore Abadan to full production.

See J. W. Williamson, In a Persian Oil Field, 2nd ed. (1930).