Mass graves in Iraq are characterized as unmarked sites containing at least six bodies. Some can be identified by mounds of earth piled above the ground or as deep pits that appear to have been filled. Some older graves are more difficult to identify, having been covered by vegetation and debris over time. Sites have been discovered in all regions of the country and contain members of every major religious and ethnic group in Iraq as well as foreign nationals, including Kuwaitis and Saudis. Over 250 sites have been reported, of which approximately 40 have been confirmed to date. Over one million Iraqis are believed to be missing in Iraq as a result of executions, wars and defections, of whom hundreds of thousands are thought to be in mass graves. Most of the graves discovered to date correspond to one of five major atrocities perpetrated by the regime.
According to Kurdistan Regional Government in Iraq, many mass graves in Kurdistan contain Iraqi Kurds, who were killed in a genocidal act just because of their ethnicity.
*1979 crackdown on Shia political parties and Shia activists. This period involved thousands of "Revolutionary Court" trials which meant groups of 200-500 Shia young men and women as young as 13 would be hoarded together and sentenced to death.
*1982 the aggressive tactics by Saddam regime to crush any Shia movements, following the kidnapping and brutal murder of a key Shia Leader Ayatollah Mohamed Baqir Al-Sadr. In this year tens of thousands of Iraq young men, women and children were sentenced to death under the accusation of joining a political party. Those who were lucky - after unimaginable torture and interrogation - would be sentenced to Lifetime imprisonment.
*The 1983 attack against Kurdish citizens belonging to the Barzani tribe, 8,000 of whom were rounded up by the regime in northern Iraq and executed in deserts at great distances from their homes.
*The 1988 Anfal campaign, during which as many as 182,000 Iraqi Kurds disappeared. Most of the men were separated from their families and were executed in deserts in the west and south-west of Iraq. The remains of some of their wives and children have also been found in mass graves.
*Chemical attacks against Kurdish villages from 1986 to 1988, including the Halabja attack, when the Iraqi Air Force dropped sarin, VX and tabun chemical agents on the civilian population, killing 5,000 people immediately and causing long-term medical problems, related deaths, and birth defects among the progeny of thousands more.
*The 1991 massacre of Iraqi Shia Muslims after the Shia uprising at the end of the Gulf war, in which tens of thousands of soldiers and civilians in regions such as Basra, Karbala, Najaf, Nasiriya, Amara and Al-Hillah were killed. Thousands of homes were demolished and vast areas of Iraq's marches were dried up causing devastating effect on the lives of people and the environment.
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Then, in March 1999, thousands more were believed to have been arrested, imprisoned and in some cases executed after a second uprising broke out after the killing of a prominent Shiite cleric.
* on 13th of May 2003, the British Newspaper the Daily Mail reported that "Iraqis pulled bound and blindfolded bodies out of a newly-discovered mass grave outside Basra, excavating a site thought to contain the remains of up to 150 Shia Muslims during Saddam's repression of a 1999 uprising"

* In May 2003, Amnesty International reported finding a grave containing 40 bodies at Abul Khasib in southern Iraq, which is almost exclusively Shia, thought to contain bodies from the 1991 Shia uprising.

*A massacre of Kurds in 1991, which targeted civilians and soldiers who fought for autonomy in northern Iraq after the Gulf war, also resulted in mass graves.