The draining of the Mesopotamian Marshes occurred in Iraq and to a smaller degree in Iran between the 1950s and 1990s to clear large areas of the marshes in the Tigris-Euphrates river system. Formerly covering an area of around 20,000 km2 (7,700 sq mi), the main sub-marshes, the Hawizeh, Central, and Hammar Marshes and all three were drained at different times for different reasons.
The draining of the Central Marshes was intended to reclaim land for agriculture and exterminate a breeding ground for the malaria-spreading mosquitoes. However, some Western and Islamist sources have described the draining as a political attempt to force the Ma'dan people out of the area through water diversion tactics.
Since the time of the Sumer, agriculture in Mesopotamia involved major melioration, including drainage and building of irrigation canals. After the collapse of the Mesopotamian civilization and the Arab conquest the territory was derelict, which resulted in the restoration of the original wetland conditions. The wetlands were gradually populated by the Marsh Arabs, or Ma'dan, who, being ignorant of the advanced agricultural techniques practiced by the Sumer and Babylonians, grew rice and grazed buffalo on the natural vegetation. At times, they had also served as a refuge for escaped slaves and serfs, such as during the Zanj Rebellion, becoming a source of instability for the whole region.
The British colonial administrators were the first to attempt to drain the marshes, motivated by their role as a breeding ground for mosquitoes and lack of apparent economic value, as well as the potential use of the water for irrigation. Prepared in 1951, The Haigh Report outlined a series of sluices, embankments and canals on the lower ends of the Tigris and Euphrates that would drain water for agriculture. These notably included the Main Outfall Drain (MOD), a large canal also referred to as the Third River, and the Nasiriyah Drainage Pump Station. Neither were completed under British rule: they were later revived by the Ba'athist government.