The city extends to the right bank of the Shatt Al Arab waterway near its confluence with the Haffar arm of the Karun river.

However, Khorramshahr was rebuilt after the war, and more recent censuses show that the population has returned to the pre-war level.

The small town known as Piyan, and later Bayan appeared in the area no sooner than the late Parthian time in the first century AD.

During the Islamic centuries, the Daylamite Buwayhid king, Panah Khusraw Adud ad-Dawlah ordered the digging of a canal to join the Karun River (which at the time emptied independently into the Persian Gulf through the Bahmanshir channel) to the Shatt al-Arab (the joint estuary of the Tigris and Euphrates rivers, known in Iran as Arvand Rud).

It was the capital of the Sheikdom of Muhammara, and until 1847, at which time it became Persian territory (according to Article II of the Treaty of Erzurum), Khorramshahr was alternately claimed and occupied by Persia and Turkey.