The term motherhouse is used by religious Order

Religious order

A religious order is a lineage of communities and organizations of people who live in some way set apart from society in accordance with their specific religious devotion, usually characterized by the principles of its founder's religious practice. The order is composed of initiates and, in some...

s and religious congregations to designate the principal house or community for that group. It can be either for the entire institute or for a region.

It would normally be where the residence and offices of the religious superior of the institute would be located. In the case where the institute is divided geographically, it is referred to as the provincial motherhouse, and would be where the regional superior would be in residence.