Umm Qasr, also known as Khawr Umm Qasr, is a port city in Iraq, on the western side of the Fao Peninsula on the shores of the Shatt al-Arab waterway which leads to the Persian Gulf. It is separated from the border of Kuwait by a small inlet; prior to the Gulf War traffic between Kuwait and Iraq flowed over a bridge here.

Umm Qasr was long a small fishing town of no great importance until a naval base was established here after the Iraqi Revolution of 1958. Modern port facilities were built here.

During the Iran-Iraq War its importance increased as fighting restricted access to other ports further east.

After the Gulf War control of the inlet leading to Umm Qasr was transferred to Kuwait, and a large trench and sand berm was constructed along the border of the two nations. Meanwhile much commerce was shifted to Umm Qasr away from Basra by deliberate Iraqi policy to punish the later city for its role in the rebellions against the reign of Saddam Hussain.

The city of Umm Qasr was one of the first Iraq cities conquered in the United States' 2003 invasion of Iraq, on March 29, 2003. Umm Qasr played an important role in the shipment of humanitarian supplies to Iraqi civilians.