The aim of this research is to shed light on grain-mills which existed in the city of Mosul because those old primitive machines were used to grind grains such wheat ,barley ,maize, sesame and so on . Mosulis have called these machines locally (al-Rahah) or (al-Tahunah).There were two kind of grain-mills according to their size: the large mills and small mills. The research divided into four axes, the first axis tackled the beginnings of the appearance and usages of grain-mills, in addition to their components and how choosing the mill-owners suitable Sites for mills according to certain terms, plus their repairing. The second axis deals with putting grain-mills under the jurisdiction of the Waqif . whiles, the third axis deals with grainmills through some registers of the Moslem religious court which have written in handwriting and deposited at the religious court .finally, the fourth axis which focuses on grain-mills through some Ottoman documents. The research arrives at some conclusions, the most important of them that there several grain-mills owned by the wealthy families of Mosul, but unfortunately, we do not know exactly identities some owners of those mills ,or that the ownership of some mills had been transferred from person to a another by selling and buying or due to death.