Posht Ab District () is a former administrative division of Zabol County, Sistan and Baluchestan province, Iran. Its capital was the city of Adimi.
In 2013, the district was separated from the county in the establishment of Nimruz County.
At the time of the 2006 National Census, the district's population was 40,434 in 8,737 households. The following census in 2011 counted 45,466 people in 10,786 households.