Khorramshahr , city (1991 pop. 34,750), Khuzestan prov., SW Iran, at the confluence of the Karun River and the Shatt al Arab, near the Persian Gulf. It is a busy port. Its development dates to the late 19th cent., when steam navigation on the Karun was started. The city was known as Muhammerah until the mid-1920s, when Reza Shah took it out of the hands of a semi-independent local sheikh and placed it under the control of the central government as Khorramshahr. It was severely attacked and partially destroyed during the Iran-Iraq War in the 1980s. The port has since been refurbished and the local economy has revived.