Investment in post-2003 Iraq refers to international efforts to rebuild the infrastructure of Iraq since the Iraq War in 2003. Along with the economic reform of Iraq, international projects have been implemented to repair and upgrade Iraqi water and sewage treatment plants, electricity production, hospitals, schools, housing, and transportation systems. Much of the work has been funded by the Iraq Relief and Reconstruction Fund, and the Coalition Provisional Authority.

A significant event for aid or investment in post-2003 Iraq was the Madrid Conference on Reconstruction on 23 October 2003, which was attended by representatives from over 25 nations. Funds assembled at this conference and from other sources have been administered by the United Nations and the World Bank under the umbrella of the International Reconstruction Fund Facility for Iraq.

While reconstruction efforts have produced some successes, problems have arisen with the implementation of internationally funded Iraq reconstruction efforts. These include inadequate security, pervasive corruption, insufficient funding and poor coordination among international agencies and local communities. Many suggest that the efforts were hampered by a poor understanding of Iraq on the part of the international community assisting with the reconstruction.

During the 1970s Iraq made extensive investment in the water sector and other infrastructure using the proceeds of oil revenue. This investment slowed during the Iran-Iraq War of 1980 to 1988, but left Iraq in 1990 with a relatively modern electrical, water supply and sewerage system. During the Gulf War of 1991 aerial bombardment caused severe damage to the electric grid that operated the pumping stations and other facilities for potable water delivery and sewage treatment. The sanctions imposed by the UN at the conclusion of the Gulf War exacerbated these problems by banning the importation of spare parts for equipment and chemicals, such as chlorine, needed for disinfection. As a result of the war and sanctions, delivery of water dropped precipitously. For example, UNICEF estimates that before 1991, 95% of urban dwellers and 75% of rural dwellers were served by modern water supply systems that delivered treated water to homes and businesses. By 1999, urban coverage had dropped to 92% and rural coverage to 46%. Individual water availability showed greater changes. Between 1990 and 2000, the daily per capita share of potable water went from 330 litres to 150 litres in Baghdad, 270 to 110 in other urban areas, and 180 to 65 in rural areas.

The March 2003 invasion of Iraq produced further degradation of Iraq's water supply, sewerage and electrical supply systems. Treatment plants, pumping stations and generating stations were stripped of their equipment, supplies and electrical wiring by looters. The once-capable cadre of engineers and operating technicians were scattered or left the country. Reconstruction efforts faced a nation with a severely degraded infrastructure.

In preparation for the October 2003 Madrid Donor Conference, the joint United Nations/World Bank team conducted an assessment of funding needs for reconstruction in Iraq during the period 2004-2007. The resulting report identified 14 sectors and associated funding needs as shown in the Table below. In addition to this US$36 billion, the Coalition Provisional Authority estimated an additional US$20 billion in need including US$5 billion for security and police and US$8 billion for oil industry infrastructure.

In 2007 the Government of Iraq and the United Nations created the International Compact with Iraq a visioning and planning entity which identified reconstruction as an essential element for meeting human needs and economic development.

Funds for Iraq reconstruction are disbursed to Iraqi ministries, non-Iraqi government agencies and various non-governmental groups. These entities then supervise the acquisition of materials and reconstruction work which is conducted by both foreign and Iraqi contractors.